What is Periodic Table?
-The periodic table of the elements is one of the most powerful icons in science: a single document that consolidates much of our knowledge of chemistry. A version hangs on the wall of nearly every chemical laboratory and lecture hall in the world. Indeed, nothing quite like it exists in the other disciplines of science.
The Story of Periodic Table
-The story of the periodic system for classifying the elements can be traced back over 200 years. Throughout its long history, the periodic table has been disputed, altered and improved as science has progressed and as new elements have been discovered [see “Making New Elements,” by Peter Armbruster and Fritz Peter Hessberger]. But despite the dramatic changes that have taken place in science over the past century—namely, the development of the theories of relativity and quantum mechanics—there has been no revolution in the basic nature of the periodic system. In some instances, new findings initially appeared to call into question the theoretical foundations of the periodic table, but each time scientists eventually managed to incorporate the results while preserving the table’s fundamental structure. Remarkably, the periodic table is thus notable both for its historical roots and for its modern relevance.
The term “periodic” reflects the fact that the elements show patterns in their chemical properties in certain regular intervals. Were it not for the simplification provided by this chart, students of chemistry would need to learn the properties of all 112 known elements. Fortunately, the periodic table allows chemists to function by mastering the properties of a handful of typical elements; all the others fall into so-called groups or families with similar chemical properties. (In the modern periodic table, a group or family corresponds to one vertical column.)
The Discovery of Periodic Table
-The discovery of the periodic system for classifying the elements represents the culmination of a number of scientific developments, rather than a sudden brainstorm on the part of one individual. Yet historians typically consider one event as marking the formal birth of the modern periodic table: on February 17, 1871, a Russian professor of chemistry, Dimitri Ivanovich Mendeleev, completed the first of his numerous periodic charts. It included 63 known elements arranged according to increasing atomic weight; Mendeleev also left spaces for as yet undiscovered elements for which he predicted atomic weights.
-JUAN CARLOS JAMISON
-The periodic table of the elements is one of the most powerful icons in science: a single document that consolidates much of our knowledge of chemistry. A version hangs on the wall of nearly every chemical laboratory and lecture hall in the world. Indeed, nothing quite like it exists in the other disciplines of science.
The Story of Periodic Table
-The story of the periodic system for classifying the elements can be traced back over 200 years. Throughout its long history, the periodic table has been disputed, altered and improved as science has progressed and as new elements have been discovered [see “Making New Elements,” by Peter Armbruster and Fritz Peter Hessberger]. But despite the dramatic changes that have taken place in science over the past century—namely, the development of the theories of relativity and quantum mechanics—there has been no revolution in the basic nature of the periodic system. In some instances, new findings initially appeared to call into question the theoretical foundations of the periodic table, but each time scientists eventually managed to incorporate the results while preserving the table’s fundamental structure. Remarkably, the periodic table is thus notable both for its historical roots and for its modern relevance.
The term “periodic” reflects the fact that the elements show patterns in their chemical properties in certain regular intervals. Were it not for the simplification provided by this chart, students of chemistry would need to learn the properties of all 112 known elements. Fortunately, the periodic table allows chemists to function by mastering the properties of a handful of typical elements; all the others fall into so-called groups or families with similar chemical properties. (In the modern periodic table, a group or family corresponds to one vertical column.)
The Discovery of Periodic Table
-The discovery of the periodic system for classifying the elements represents the culmination of a number of scientific developments, rather than a sudden brainstorm on the part of one individual. Yet historians typically consider one event as marking the formal birth of the modern periodic table: on February 17, 1871, a Russian professor of chemistry, Dimitri Ivanovich Mendeleev, completed the first of his numerous periodic charts. It included 63 known elements arranged according to increasing atomic weight; Mendeleev also left spaces for as yet undiscovered elements for which he predicted atomic weights.
-JUAN CARLOS JAMISON
The periodic table we use today is based on the one devised and published by Dmitri Mendeleev in 1869. Mendeleev found he could arrange the 65 elements then known in a grid or table so that each element had:
1. A higher atomic weight than the one on its left. For example, magnesium (atomic weight 24.3) is placed to the right of sodium (atomic weight 23.0)
2. Similar chemical properties to other elements in the same column - in other words similar chemical reactions. Magnesium, for example, is placed in the alkali earths' column.
Mendeleev realized that the table in front of him lay at the very heart of chemistry. And more than that, Mendeleev saw that his table was incomplete - there were spaces where elements should be, but no-one had discovered them.
Just as Adams and Le Verrier could be said to have discovered the planet Neptune on paper, Mendeleev could be said to have discovered germanium on paper. He called this new elements eka-silicon, after observing a gap in the periodic table between silicon and tin.
Similarly, Mendeleev discovered gallium (eka-aluminum) and scandium (eka-boron) on paper, because he predicted their existence and their properties before their actual discoveries.
Although Mendeleev had made a crucial breakthrough, he made little further progress. With the benefit of hindsight, we know that Mendeleev's periodic table was underpinned by false reasoning. Mendeleev believed, incorrectly, that chemical properties were determined by atomic weight. Of course, this was perfectly reasonable when we consider scientific knowledge in 1869.
In 1869 the electron itself had not been discovered - that happened 27 years later, in 1896.
In fact, it took 44 years for the correct explanation of the regular patterns in Mendeleev's periodic table to be found.
-CEEJAY IBARRA
-JOANNABEL PAMINTUAN
1. A higher atomic weight than the one on its left. For example, magnesium (atomic weight 24.3) is placed to the right of sodium (atomic weight 23.0)
2. Similar chemical properties to other elements in the same column - in other words similar chemical reactions. Magnesium, for example, is placed in the alkali earths' column.
Mendeleev realized that the table in front of him lay at the very heart of chemistry. And more than that, Mendeleev saw that his table was incomplete - there were spaces where elements should be, but no-one had discovered them.
Just as Adams and Le Verrier could be said to have discovered the planet Neptune on paper, Mendeleev could be said to have discovered germanium on paper. He called this new elements eka-silicon, after observing a gap in the periodic table between silicon and tin.
Similarly, Mendeleev discovered gallium (eka-aluminum) and scandium (eka-boron) on paper, because he predicted their existence and their properties before their actual discoveries.
Although Mendeleev had made a crucial breakthrough, he made little further progress. With the benefit of hindsight, we know that Mendeleev's periodic table was underpinned by false reasoning. Mendeleev believed, incorrectly, that chemical properties were determined by atomic weight. Of course, this was perfectly reasonable when we consider scientific knowledge in 1869.
In 1869 the electron itself had not been discovered - that happened 27 years later, in 1896.
In fact, it took 44 years for the correct explanation of the regular patterns in Mendeleev's periodic table to be found.
-CEEJAY IBARRA
-JOANNABEL PAMINTUAN
A BRIEF HISTORY OF THE DEVELOPMENT OF PERIODIC TABLE
Although Dmitri Mendeleev is often considered the "father" of the periodic table, the work of many scientists contributed to its present form.
In the Beginning A necessary prerequisite to the construction of the periodic table was the discovery of the individual elements. Although elements such as gold, silver, tin, copper, lead and mercury have been known since antiquity, the first scientific discovery of an element occurred in 1649 when Hennig Brand discovered phosphorous. During the next 200 years, a vast body of knowledge concerning the properties of elements and their compounds was acquired by chemists (viewa 1790 article on the elements). By 1869, a total of 63 elements had been discovered. As the number of known elements grew, scientists began to recognize patterns in properties and began to develop classification schemes.
Law of Triads In 1817 Johann Dobereiner noticed that the atomic weight of strontium fell midway between the weights of calcium and barium, elements possessing similar chemical properties. In 1829, after discovering the halogen triad composed of chlorine, bromine, and iodine and the alkali metal triad of lithium, sodium and potassium he proposed that nature contained triads of elements the middle element had properties that were an average of the other two members when ordered by the atomic weight (the Law of Triads).
This new idea of triads became a popular area of study. Between 1829 and 1858 a number of scientists (Jean Baptiste Dumas, Leopold Gmelin, Ernst Lenssen, Max von Pettenkofer, and J.P. Cooke) found that these types of chemical relationships extended beyond the triad. During this time fluorine was added to the halogen group; oxygen, sulfur,selenium and tellurium were grouped into a family while nitrogen, phosphorus, arsenic, antimony, and bismuth were classified as another. Unfortunately, research in this area was hampered by the fact that accurate values of were not always available.
First Attempts At Designing a Periodic Table If a periodic table is regarded as an ordering of the chemical elements demonstrating the periodicity of chemical and physical properties, credit for the first periodic table (published in 1862) probably should be given to a French geologist, A.E.Beguyer de Chancourtois. De Chancourtois transcribed a list of the elements positioned on a cylinder in terms of increasing atomic weight. When the cylinder was constructed so that 16 mass units could be written on the cylinder per turn, closely related elements were lined up vertically. This led de Chancourtois to propose that "the properties of the elements are the properties of numbers." De Chancourtois was first to recognize that elemental properties reoccur every seven elements, and using this chart, he was able to predict the stoichiometry of several metallic oxides. Unfortunately, his chart included some ions and compounds in addition to elements.
Law of Octaves John Newlands, an English chemist, wrote a paper in 1863 which classified the 56 established elements into 11 groups based on similar physical properties, noting that many pairs of similar elements existed which differed by some multiple of eight in atomic weight. In 1864 Newlands published his version of the periodic table and proposed the Law of Octaves (by analogy with the seven intervals of the musical scale). This law stated that any given element will exhibit analogous behavior to the eighth element following it in the table.
Who Is The Father of the Periodic Table? There has been some disagreement about who deserves credit for being the "father" of the periodic table, the German Lothar Meyer (pictured here) or the Russian Dmitri Mendeleev. Both chemists produced remarkably similar results at the same time working independently of one another. Meyer's 1864 textbook included a rather abbreviated version of a periodic table used to classify the elements. This consisted of about half of the known elements listed in order of their atomic weight and demonstrated periodic valence chages as a function of atomic weight. In 1868, Meyer constructed an extended table which he gave to a colleague for evaluation. Unfortunately for Meyer, Mendeleev's table became available to the scientific community via publication (1869) before Meyer's appeared (1870).
Dmitri Ivanovich Mendeleev (1834-1907), the youngest of 17 children was born in the Siberian town of Tobol'sk where his father was a teacher of Russian literature and philosophy (portrait by Ilyia Repin). Mendeleev was not considered an outstanding student in his early education partly due to his dislike of the classical languages that were an important educational requirement at the time even though he showed prowess in mathematics and science. After his father's death, he and his mother moved to St. Petersburg to pursue a university education. After being denied admission to both the University of Moscow and St. Petersburg University because of his provincial background and unexceptional academic background, he finally earned a place at the Main Pedagogical Institute (St. Petersburg Institute). Upon graduation, Mendeleev took a position teaching science in a gymnasium. After a time as a teacher, he was admitted to graduate work at St. Petersburg University where he earned a Master's degree in 1856. Mendeleev so impressed his instructors that he was retained to lecture in chemistry. After spending 1859 and 1860 in Germany furthering his chemical studies, he secured a position as professor of chemistry at St. Petersburg University, a position he retained until 1890. While writing a textbook on systematic inorganic chemistry, Principles of Chemistry, which appeared in thirteen editions the last being in 1947, Mendeleev organized his material in terms of the families of the known elements which displayed similar properties. The first part of the text was devoted to the well known chemistry of the halogens. Next, he chose to cover the chemistry of the metallic elements in order of combining power -- alkali metals first (combining power of one), alkaline earths (two), etc. However, it was difficult to classify metals such as copper and mercury which had multiple combining powers, sometimes one and other times two. While tryuing to sort out this dilema, Mendeleev noticed patterns in the properties and atomic weights of halogens, alkali metals and alkaline metals. He observed similarities between the series Cl-K-Ca , Br-/Rb-Sr and I-Cs-Ba. In an effort to extend this pattern to other elements, he created a card for each of the 63 known elements. Each card contained the element's symbol, atomic weight and its characteristic chemical and physical properties. When Mendeleev arranged the cards on a table in order of ascending atomic weight grouping elements of similar properties together in a manner not unlike the card arrangement in his favorite solitare card game, patience, the periodic table was formed. From this table, Mendeleev developed his statement of the periodic law and published his work On the Relationship of the Properties of the Elements to their Atomic Weights in 1869. The advantage of Mendeleev's table over previous attempts was that it exhibited similarities not only in small units such as the triads, but showed similarities in an entire network of vertical, horizontal, and diagonal relationships. In 1906, Mendeleev came within one vote of being awarded the Nobel Prize for his work.
At the time that Mendeleev developed his periodic table since the experimentally determined atomic masses were not always accurate, he reordered elements despite their accepted masses. For example, he changed the weight of beryllium from 14 to 9. This placed beryllium into Group 2 above magnesium whose properties it more closely resembled than where it had been located above nitrogen. In all Mendeleev found that 17 elements had to be moved to new positions from those indicated strictly by atomic weight for their properties to correlate with other elements. These changes indicated that there were errors in the accepted atomic weights of some elements (atomic weights were calculated from combining weights, the weight of an element that combines with a given weight of a standard.) However, even after corrections were made by redetermining atomic weights, some elements still needed to be placed out of order of their atomic weights. From the gaps present in his table, Mendeleev predicted the existence and properties of unknown elements which he called eka-aluminum, eka-boron, and eka-silicon. The elements gallium, scandium and germanium were found later to fit his predictions quite well. In addition to the fact that Mendeleev's table was published before Meyers', his work was more extensive predicting new or missing elements. In all Mendeleev predicted the existence of 10 new elements, of which seven were eventually discovered -- the other three, atomic weights 45, 146 and 175 do not exist. He also was incorrect in suggesting that the element pairs of argon-potassium, cobalt-nickel and tellurium-iodine should be interchanged in position due to inaccurate atomic weights. Although these elements did need to be interchanged, it was because of a flaw in the reasoning that periodicity is a function of atomic weight.
Discovery of the Noble Gases In 1895 Lord Rayleigh reported the discovery of a new gaseous element named argon which proved to be chemically inert. This element did not fit any of the known periodic groups. In 1898, William Ramsey suggested that argon be placed into the periodic table between chlorine and potassium in a family with helium, despite the fact that argon's atomic weight was greater than that of potassium. This group was termed the "zero" group due to the zero valency of the elements. Ramsey accurately predicted the future discovery and properties neon.
Atomic Structure and the Periodic Table Although Mendeleev's table demonstrated the periodic nature of the elements, it remained for the discoveries of scientists of the 20th Century to explain why the properties of the elements recur periodically.
In 1911 Ernest Rutherford published studies of the scattering of alpha particles by heavy atom nuclei which led to the determination of nuclear charge. He demonstrated that the nuclear charge on a nucleus was proportional to the atomic weight of the element. Also in 1911, A. van den Broek in a series of two papers proposed that the atomic weight of an element was approximately equal to the charge on an atom. This charge, later termed the atomic number, could be used to number the elements within the periodic table. In 1913, Henry Moseley (see a picture) published the results of his measurements of the wavelengths of the x-ray spectral lines of a number of elements which showed that the ordering of the wavelengths of the x-ray emissions of the elements coincided with the ordering of the elements by atomic number. With the discovery of isotopes of the elements, it became apparent that atomic weight was not the significant player in the periodic law as Mendeleev, Meyers and others had proposed, but rather, the properties of the elements varied periodically with atomic number.
The question of why the periodic law exists was answered as scientists developed an understanding of the electronic structure of the elements beginning with Niels Bohr's studies of the organization of electrons into shells through G.N. Lewis' (see a picture) discoveries of bonding electron pairs.
Source: http://www.wou.edu/las/physci/ch412/perhist.htm
-Abigail D. Damaso 8-Avocado
The Beginnings of the Periodic Table
Before written history, people were aware of some of the elements in the periodic table. Elements such as gold (Au), silver (Ag), copper (Cu), lead (Pb), tin (Sn), and mercury (Hg).
It wasn't until 1649, however, until the first element was discovered through scientific inquiry by Hennig Brand . That element was phosphorous (P).
By 1869, 63 elements had been discovered.
Creating Some Early Blocks for the Periodic Table
Between 1817-1829, Johann Dobereiner began to group elements with similar properties in groups of three or triads. This began in 1817 when he noticed that the atomic weights of strontium, Sr, was halfway between the weights of calcium and barium. These elements possessed similar chemical properties. By 1829, he had discovered the a halogen triad made up of chlorine, bromine, and iodine and a alkali metal triad of lithium, sodium and potassium. He postulated that nature contained triads of elements in which the middle element had properties that were an average of the other two elements. Later, other scientists found other triads and recognized that elements could be grouped into set large than three. The poor accuracy of measurements such as that of atomic weights hindered grouping more elements.
Precursors to the Periodic Table
In 1862, A.E.Beguyer de Chancourtois was the first person to make use of atomic weights to reveal that the elements were arranged according to their atomic weights with similar elements occurring at regular intervals. He drew the elements as a continuous spiral around a cylinder divided into 16 parts. A list of elements was wrapped around a cylinder so that several sets of similar elements lined up, creating the first geometric representation of the periodic law.
In 1863, John Newlands, an English chemist, proposed the Law of Octaves which stated that elements repeated their chemical properties every eighth element.
The musical analogy was ridiculed at the time, but was found to be insightful after the work of Mendeleev and Meyer were published.
The Fathers of the Periodic Table
Lothar Meyer and Dmitri Ivanovich Mendeleev independently produced remarkably similar versions of the periodic table of elements at the essentially the same time.
Meyer's 1864 textbook included a abbreviated version of a periodic table used to classify about half of the known elements. In 1868, Meyer constructed an extended table which he gave to a colleague for evaluation. This table unfortunately was not published until 1870, a year after Mendeleev's table was published.
Mendeleev periodic table appeared in his work "On the Relationship of the Properties of the Elements to their Atomic Weights" in 1869. Mendeleev placed many elements out of order based on their accepted atomic weights at the time.
Mendeleev predicted the existence and properties of unknown elements which he called eka-aluminum, eka-boron, and eka-silicon. The elements gallium, scandium and germanium were found later to fit his predictions quite well.
The Modern Periodic Table
Glenn Seaborg discovered the transuranium elements, atomic numbers 94 to 102. The completion of the actinide series allow Seaborg to redesign the periodic table into it current form. Both the lanthanide and actinide series of elements were placed under the rest of the periodic table. These elements technically should be placed between the alkaline earth metals and the transition metals, however, since this would make the periodic table too wide, they were placed below the rest of the elements.
Dr. Seaborg and his colleagues are also responsible for the identification of more than 100 isotopes of elements.
-GAVRIEL DONASCO
Before written history, people were aware of some of the elements in the periodic table. Elements such as gold (Au), silver (Ag), copper (Cu), lead (Pb), tin (Sn), and mercury (Hg).
It wasn't until 1649, however, until the first element was discovered through scientific inquiry by Hennig Brand . That element was phosphorous (P).
By 1869, 63 elements had been discovered.
Creating Some Early Blocks for the Periodic Table
Between 1817-1829, Johann Dobereiner began to group elements with similar properties in groups of three or triads. This began in 1817 when he noticed that the atomic weights of strontium, Sr, was halfway between the weights of calcium and barium. These elements possessed similar chemical properties. By 1829, he had discovered the a halogen triad made up of chlorine, bromine, and iodine and a alkali metal triad of lithium, sodium and potassium. He postulated that nature contained triads of elements in which the middle element had properties that were an average of the other two elements. Later, other scientists found other triads and recognized that elements could be grouped into set large than three. The poor accuracy of measurements such as that of atomic weights hindered grouping more elements.
Precursors to the Periodic Table
In 1862, A.E.Beguyer de Chancourtois was the first person to make use of atomic weights to reveal that the elements were arranged according to their atomic weights with similar elements occurring at regular intervals. He drew the elements as a continuous spiral around a cylinder divided into 16 parts. A list of elements was wrapped around a cylinder so that several sets of similar elements lined up, creating the first geometric representation of the periodic law.
In 1863, John Newlands, an English chemist, proposed the Law of Octaves which stated that elements repeated their chemical properties every eighth element.
The musical analogy was ridiculed at the time, but was found to be insightful after the work of Mendeleev and Meyer were published.
The Fathers of the Periodic Table
Lothar Meyer and Dmitri Ivanovich Mendeleev independently produced remarkably similar versions of the periodic table of elements at the essentially the same time.
Meyer's 1864 textbook included a abbreviated version of a periodic table used to classify about half of the known elements. In 1868, Meyer constructed an extended table which he gave to a colleague for evaluation. This table unfortunately was not published until 1870, a year after Mendeleev's table was published.
Mendeleev periodic table appeared in his work "On the Relationship of the Properties of the Elements to their Atomic Weights" in 1869. Mendeleev placed many elements out of order based on their accepted atomic weights at the time.
Mendeleev predicted the existence and properties of unknown elements which he called eka-aluminum, eka-boron, and eka-silicon. The elements gallium, scandium and germanium were found later to fit his predictions quite well.
The Modern Periodic Table
Glenn Seaborg discovered the transuranium elements, atomic numbers 94 to 102. The completion of the actinide series allow Seaborg to redesign the periodic table into it current form. Both the lanthanide and actinide series of elements were placed under the rest of the periodic table. These elements technically should be placed between the alkaline earth metals and the transition metals, however, since this would make the periodic table too wide, they were placed below the rest of the elements.
Dr. Seaborg and his colleagues are also responsible for the identification of more than 100 isotopes of elements.
-GAVRIEL DONASCO
The periodic table: how elements get their names
Most people could name many of the elements, but how many of us know how they got those names?
Each of the 115 known chemical elements was discovered over the last few thousand years, from before recorded history began to the nuclear laboratories of the 21st century.
Their chosen names were influenced by an ever changing mix of language, culture and our understanding of chemistry.
So how did they get these names? And why do they end in -ium?
British scientists and the elements
· Several elements' names have Anglo-Saxon language origins, including gold, iron, copper and silver.
· These metals were known long before they got these names, however. Gold can be found in its pure form in nature and although iron is usually found in ores which require smelting, the earliest known iron artefacts, from 3500 BCE, derive from purer metal from meteorites.
· The Latin names of these elements are commemorated in their atomic symbols, Au (aurum) for gold and Fe (ferrum) for iron.
The Romans began the practise of element names ending in "-um," with Victorian scientists continuing the trend.
Element of uncertainty
Since 1947, the International Union of Pure and Applied Chemistry (IUPAC) has had the responsibility for approving elements' names, and deciding the single internationally recognised symbol for each element.
Before this, there were multiple historical occasions of elements being given several names, usually due to simultaneous discovery or uncertainty over a discovery.
The name of element 41 was not agreed for 150 years. It was called columbium in America and niobium in Europe until IUPAC finally decided the official name would be niobium in 1949.
Dr Fabienne Meyers, Associate Director of IUPAC, explains the current naming process: To start with, "the discoverers are invited to propose a name and a symbol."
"For linguistic consistency, the recommended practice is that all new elements should end in '-ium'," she adds.
"Since the sake of naming an element is essentially to avoid confusion, it is important to ensure that the proposed name is unique and has not been used earlier even unofficially or temporarily for a different element."
"After examination and acceptance by the division - which includes a public review period of five months - the name and symbol are then submitted to the IUPAC Council for approval."
The name is then published in the scientific journal Pure and Applied Chemistry.
Actinium to zirconium
A common source of names both now and historically, over a quarter of the elements are named after a place, often where they were discovered or synthesised.
These places range in size from continents (europium) and countries (americium, francium, polonium) to the the Scottish village Strontian (strontium).
Because of the great wealth of discoveries made there, four elements are named after the Swedish mining village, Ytterby (ytterbium, yttrium, erbium and terbium).
There is just one element that wasn't first discovered on Earth, and it too is named after its place of the discovery - helium, from the Greek word for Sun, helios.
Myth and legend
Dmitri Mendeleev published the periodic table in its modern form.
About a dozen elements take their name directly from legends, including titanium, arsenic and tantalum.
Nickel and cobalt are named after 'devil' and 'kobold', from the Germanic folk belief that malign creatures snuck into mines to replace valuable and similar-looking copper and silver ores with these less valuable ones.
In 1949 the artificial element Promethium was named after Prometheus, the man in Greek legend punished with eternal torture for stealing fire from the gods, as a reference to the great difficulty and sacrifice needed to synthesise new elements.
Eponymous elements
Modestly, no discoverer has ever named an element after him or herself, but several scientists have been honoured by having elements named after them. These include curium, einsteinium and fermium.
Seaborgium, named after American chemist Glenn Seaborg, was the first element to be named after a living scientist.
There is also mendelevium, named after Dmitri Mendeleev, the Russian scientist who established the first periodic table in 1869, and fitted the known elements into their places in the table based on their properties.
Elemental techniques
Sample of chlorine created by Humphry Davy in 1810. It is named after the Greek word for green.
Fifty elements were discovered in the 19th Century, the greatest number of any century. By comparison, twenty nine elements were discovered in the 20th Century, and five new ones have been synthesised so far in the 21st.
Frank James, Professor of the History of Science at The Royal Institution in London, where several elements were discovered, says that the contribution of British scientists was very important.
"Using electro-chemical methods, Humphry Davy either isolated or demonstrated the elemental nature of a total of nine chemical elements naming most of them in the process, such as sodium, potassium and chlorine."
British scientist William Ramsay used a powerful new technique, spectroscopy, to discover the noble gases, a group of elements which had evaded discovery due to their lack of reactivity. He used Greek words to name neon (new), xenon (stranger), krypton (hidden), and argon (inactive).
Colours and sense
Colours are a name source for nine elements. Each element can be identified by the colours it emits using spectroscopy, and several elements are named after the brightest colour they emit, including indium and rubidium.
Visible traits are a major source of names, but the other senses are represented too: osmium and bromine are named for their smell, and aluminium is named after the Latin word for the bitter tasting chemical in which it was first discovered, alum.
Spectroscopy
Each element can be made to emit a unique spectrum of light which identifies it like a fingerprint. Helium's emission spectrum is shown above.
Ununpentium onwards
The newest element to be experimentally confirmed, element 115, will be called ununpentium until an official name is decided, and 114 (Flerovium) and 116 (Livermorium) were named in 2012.
IUPAC's Dr Meyers explains that although all recent elements have been named after people and places, "a mythological concept or character, a mineral or a property of the element could also be used as the root for an acceptable name."
And with no shortage of eminent scientists and important centres of science as inspiration, new names will always retain an element of surprise.
BY: Sofia Andrea A. Sabado
Most people could name many of the elements, but how many of us know how they got those names?
Each of the 115 known chemical elements was discovered over the last few thousand years, from before recorded history began to the nuclear laboratories of the 21st century.
Their chosen names were influenced by an ever changing mix of language, culture and our understanding of chemistry.
So how did they get these names? And why do they end in -ium?
British scientists and the elements
- Humphry Davy discovered nine elements using electrolysis - the splitting up of compounds into elements by applying electricity.
- William Ramsay discovered a new group of unreactive elements using spectroscopy, now called the noble gases.
- William Crookes identified helium for the first time, and also discovered thallium.
· Several elements' names have Anglo-Saxon language origins, including gold, iron, copper and silver.
· These metals were known long before they got these names, however. Gold can be found in its pure form in nature and although iron is usually found in ores which require smelting, the earliest known iron artefacts, from 3500 BCE, derive from purer metal from meteorites.
· The Latin names of these elements are commemorated in their atomic symbols, Au (aurum) for gold and Fe (ferrum) for iron.
The Romans began the practise of element names ending in "-um," with Victorian scientists continuing the trend.
Element of uncertainty
Since 1947, the International Union of Pure and Applied Chemistry (IUPAC) has had the responsibility for approving elements' names, and deciding the single internationally recognised symbol for each element.
Before this, there were multiple historical occasions of elements being given several names, usually due to simultaneous discovery or uncertainty over a discovery.
The name of element 41 was not agreed for 150 years. It was called columbium in America and niobium in Europe until IUPAC finally decided the official name would be niobium in 1949.
Dr Fabienne Meyers, Associate Director of IUPAC, explains the current naming process: To start with, "the discoverers are invited to propose a name and a symbol."
"For linguistic consistency, the recommended practice is that all new elements should end in '-ium'," she adds.
"Since the sake of naming an element is essentially to avoid confusion, it is important to ensure that the proposed name is unique and has not been used earlier even unofficially or temporarily for a different element."
"After examination and acceptance by the division - which includes a public review period of five months - the name and symbol are then submitted to the IUPAC Council for approval."
The name is then published in the scientific journal Pure and Applied Chemistry.
Actinium to zirconium
A common source of names both now and historically, over a quarter of the elements are named after a place, often where they were discovered or synthesised.
These places range in size from continents (europium) and countries (americium, francium, polonium) to the the Scottish village Strontian (strontium).
Because of the great wealth of discoveries made there, four elements are named after the Swedish mining village, Ytterby (ytterbium, yttrium, erbium and terbium).
There is just one element that wasn't first discovered on Earth, and it too is named after its place of the discovery - helium, from the Greek word for Sun, helios.
Myth and legend
Dmitri Mendeleev published the periodic table in its modern form.
About a dozen elements take their name directly from legends, including titanium, arsenic and tantalum.
Nickel and cobalt are named after 'devil' and 'kobold', from the Germanic folk belief that malign creatures snuck into mines to replace valuable and similar-looking copper and silver ores with these less valuable ones.
In 1949 the artificial element Promethium was named after Prometheus, the man in Greek legend punished with eternal torture for stealing fire from the gods, as a reference to the great difficulty and sacrifice needed to synthesise new elements.
Eponymous elements
Modestly, no discoverer has ever named an element after him or herself, but several scientists have been honoured by having elements named after them. These include curium, einsteinium and fermium.
Seaborgium, named after American chemist Glenn Seaborg, was the first element to be named after a living scientist.
There is also mendelevium, named after Dmitri Mendeleev, the Russian scientist who established the first periodic table in 1869, and fitted the known elements into their places in the table based on their properties.
Elemental techniques
Sample of chlorine created by Humphry Davy in 1810. It is named after the Greek word for green.
Fifty elements were discovered in the 19th Century, the greatest number of any century. By comparison, twenty nine elements were discovered in the 20th Century, and five new ones have been synthesised so far in the 21st.
Frank James, Professor of the History of Science at The Royal Institution in London, where several elements were discovered, says that the contribution of British scientists was very important.
"Using electro-chemical methods, Humphry Davy either isolated or demonstrated the elemental nature of a total of nine chemical elements naming most of them in the process, such as sodium, potassium and chlorine."
British scientist William Ramsay used a powerful new technique, spectroscopy, to discover the noble gases, a group of elements which had evaded discovery due to their lack of reactivity. He used Greek words to name neon (new), xenon (stranger), krypton (hidden), and argon (inactive).
Colours and sense
Colours are a name source for nine elements. Each element can be identified by the colours it emits using spectroscopy, and several elements are named after the brightest colour they emit, including indium and rubidium.
Visible traits are a major source of names, but the other senses are represented too: osmium and bromine are named for their smell, and aluminium is named after the Latin word for the bitter tasting chemical in which it was first discovered, alum.
Spectroscopy
Each element can be made to emit a unique spectrum of light which identifies it like a fingerprint. Helium's emission spectrum is shown above.
Ununpentium onwards
The newest element to be experimentally confirmed, element 115, will be called ununpentium until an official name is decided, and 114 (Flerovium) and 116 (Livermorium) were named in 2012.
IUPAC's Dr Meyers explains that although all recent elements have been named after people and places, "a mythological concept or character, a mineral or a property of the element could also be used as the root for an acceptable name."
And with no shortage of eminent scientists and important centres of science as inspiration, new names will always retain an element of surprise.
BY: Sofia Andrea A. Sabado
The Importance of a Periodic Table
by Wanda Thibodeaux, Demand Media
The periodic table of the elements has gone through numerous revisions over the years as scientists have gained more knowledge about the atomic structure of the elements. The most recent version of the periodic table provides useful information that, directly or indirectly, affects everyone.
Identification
The periodic table of the elements describes the atomic structure of all elements that are known to mankind. For instance, by looking at the periodic table, a person can find out how many electrons the element has and how much it weighs. Each element has its own separate set of such data; no two elements are the same. Thus, if someone is uncertain what matter he has, he can look at the atomic structure of the material, compare it to the information in the periodic table, and identify the material by matching it to the element on the table with the same data.
Properties
The elements in the periodic table are grouped in particular families and periods (vertical and horizontal rows). The elements in each family or period have similar or dissimilar characteristics. The table thus is a quick reference as to what elements may behave the same chemically or which may have similar weights or atomic structures.
Experiments
The information contained in the periodic table (such as atomic weight and what elements are similar) lets scientists know how the elements are put together atomically and how they will behave. Once scientists understand this data, they can apply it in experiments. These experiments can be something as simple as combining hydrogen and oxygen to make water, or they can be as dramatic as making a hydrogen bomb.
Classification
The periodic table can be used to identify the matter already discovered by mankind. However, if new matter is discovered, then the atomic structure of the new matter can be compared to the elements in the table in order to classify the new material. Scientists can use the data in the table to figure out how the new matter may behave or what elements to which the new matter may be similar through this comparison.
Historical Perspective
Scientists can use the information in the periodic table to know when elements have been acted upon in some way. For instance, if scientists know that the basic form of an element has a particular number of neutrons, then they know that something has to have happened to the element if an isotope (an atom with the same number of protons but a different number of neutrons than the base element) is discovered. They may not know exactly what caused the isotope to form, but they can know with certainty that something did occur. This gives historical perspective.
Source: http://classroom.synonym.com/importance-periodic-table-2475.html
-Jhemem Palattao
by Wanda Thibodeaux, Demand Media
The periodic table of the elements has gone through numerous revisions over the years as scientists have gained more knowledge about the atomic structure of the elements. The most recent version of the periodic table provides useful information that, directly or indirectly, affects everyone.
Identification
The periodic table of the elements describes the atomic structure of all elements that are known to mankind. For instance, by looking at the periodic table, a person can find out how many electrons the element has and how much it weighs. Each element has its own separate set of such data; no two elements are the same. Thus, if someone is uncertain what matter he has, he can look at the atomic structure of the material, compare it to the information in the periodic table, and identify the material by matching it to the element on the table with the same data.
Properties
The elements in the periodic table are grouped in particular families and periods (vertical and horizontal rows). The elements in each family or period have similar or dissimilar characteristics. The table thus is a quick reference as to what elements may behave the same chemically or which may have similar weights or atomic structures.
Experiments
The information contained in the periodic table (such as atomic weight and what elements are similar) lets scientists know how the elements are put together atomically and how they will behave. Once scientists understand this data, they can apply it in experiments. These experiments can be something as simple as combining hydrogen and oxygen to make water, or they can be as dramatic as making a hydrogen bomb.
Classification
The periodic table can be used to identify the matter already discovered by mankind. However, if new matter is discovered, then the atomic structure of the new matter can be compared to the elements in the table in order to classify the new material. Scientists can use the data in the table to figure out how the new matter may behave or what elements to which the new matter may be similar through this comparison.
Historical Perspective
Scientists can use the information in the periodic table to know when elements have been acted upon in some way. For instance, if scientists know that the basic form of an element has a particular number of neutrons, then they know that something has to have happened to the element if an isotope (an atom with the same number of protons but a different number of neutrons than the base element) is discovered. They may not know exactly what caused the isotope to form, but they can know with certainty that something did occur. This gives historical perspective.
Source: http://classroom.synonym.com/importance-periodic-table-2475.html
-Jhemem Palattao
The Periodic Table of Elements
We people use many of the components of the periodic table but we do not know how or what they are made of. So here’s an example.
The Atom and its composition.
First of all the periodic table consists of the so called “The Periodic Law” that was proposed by Henry J.G Moseley, which states that the elements at the periodic table are arranged by its Atomic no.
Atomic No. – Atomic Number is the protons found in the nucleus of an atom. Also it is represented by the symbol “Z”.
Atom is always found in our surroundings yet not in its usual form.
We state that Matter consists of Atoms that has its own Sub-atomic parts.
The sub-atomic parts are those of the protons, electrons, neutrons.
Each of the given sub-atomic parts has its own kind of mass and composition.
Introduction
The Bohr’s Model is out-dated but depicts the three basic sub - atomic particles in a comprehendible way. Electron clouds are better representations of where electrons are found. The darker areas represent where the electrons will have a higher probability of being located and the lighter areas represent where they are less likely to be found.
-GABRIELE DE LARA
We people use many of the components of the periodic table but we do not know how or what they are made of. So here’s an example.
The Atom and its composition.
First of all the periodic table consists of the so called “The Periodic Law” that was proposed by Henry J.G Moseley, which states that the elements at the periodic table are arranged by its Atomic no.
Atomic No. – Atomic Number is the protons found in the nucleus of an atom. Also it is represented by the symbol “Z”.
Atom is always found in our surroundings yet not in its usual form.
We state that Matter consists of Atoms that has its own Sub-atomic parts.
The sub-atomic parts are those of the protons, electrons, neutrons.
Each of the given sub-atomic parts has its own kind of mass and composition.
Introduction
The Bohr’s Model is out-dated but depicts the three basic sub - atomic particles in a comprehendible way. Electron clouds are better representations of where electrons are found. The darker areas represent where the electrons will have a higher probability of being located and the lighter areas represent where they are less likely to be found.
-GABRIELE DE LARA
Periodic table of elements by Liezl B. Verdeflor
Periodic table is a table consisting different chemical elements on our Earth. Elements are listed in order of increasing atomic number. Elements are also the building blocks for all matter. It is lined up so that elements which are similar properties are arranged in the same column as each other. The Periodic Table is one of the most useful tools of chemistry. All of the elements are strictly man-made. The International Union of Pure Applied Chemistry, IUPAC, revises the periodic table as new data. At the time, the most recent version of the periodic table was approved 19 February 2010.
The row of the periodic table is what you called periods. An element's period number is the highest unexcited energy level for an electron of that element. Columns of elements help to identify groups in the periodic table. Elements within group share common properties and often have the same outer electron arrangement and those outer electrons are also called valence electrons. They are the ones involved in chemical bonds with other elements.
We sometimes use the terms atom and element to mean the same thing. Always remember that atom is the general term and everything is made up of atoms. The term element is used to describe atoms.
We are made up of billions and billions of atoms but we probably won't find more than 40 elements in our body. Chemists have figured out that over 95% of our body is made up of hydrogen (H), carbon (C), nitrogen, oxygen, phosphorus (P), and calcium (Ca). Hydrogen and helium are two special elements on the periodic table. To scientists, hydrogen is sometimes missing an electron, and sometimes has an extra one while Helium is different among the other elements because it can only have two electrons in its outer shell.
-LIEZL VERDEFLOR
Periodic table is a table consisting different chemical elements on our Earth. Elements are listed in order of increasing atomic number. Elements are also the building blocks for all matter. It is lined up so that elements which are similar properties are arranged in the same column as each other. The Periodic Table is one of the most useful tools of chemistry. All of the elements are strictly man-made. The International Union of Pure Applied Chemistry, IUPAC, revises the periodic table as new data. At the time, the most recent version of the periodic table was approved 19 February 2010.
The row of the periodic table is what you called periods. An element's period number is the highest unexcited energy level for an electron of that element. Columns of elements help to identify groups in the periodic table. Elements within group share common properties and often have the same outer electron arrangement and those outer electrons are also called valence electrons. They are the ones involved in chemical bonds with other elements.
We sometimes use the terms atom and element to mean the same thing. Always remember that atom is the general term and everything is made up of atoms. The term element is used to describe atoms.
We are made up of billions and billions of atoms but we probably won't find more than 40 elements in our body. Chemists have figured out that over 95% of our body is made up of hydrogen (H), carbon (C), nitrogen, oxygen, phosphorus (P), and calcium (Ca). Hydrogen and helium are two special elements on the periodic table. To scientists, hydrogen is sometimes missing an electron, and sometimes has an extra one while Helium is different among the other elements because it can only have two electrons in its outer shell.
-LIEZL VERDEFLOR
Periodic Table of Elements
The periodic table is a table of the chemical elements in which the elements are arranged by order of atomic number.
THE PERIODIC LAW
By the first half of the nineteenth century, the concept of elements was already better under stood, improved analytical techniques had been invented which allowed for new substances to be identified, and more processes for the separation of some elements from their compounds had been introduced. These developments led to surge in the discovery of elements. By the 1860s,more than 60 elements had been isolated and identified.
Chemists began to notice that some elements had similar behavior. They organized the increasing number of known elements to better understand them and put their properties to good use.
Julius Lothar Meyer(1830-1895), a German, and Dmitri Ivanovich Mendeleev(1834-1907), a Russian, are the chemists credited for the discovery of the periodic law. They noted that, if the elements were arranged on the basis of increasing atomic mass, elements with similar properties would occur periodically, or at regular intervals. Mendeleev is credited for pursuing this idea of periodic behavior and he went on to correctly predict the existence of elements that were still undiscovered at that time.
METALS, NON METALS AND METALLOIDS
Most of the 117 elements are metals. The metals are located on the left side of the table, except for one, hydrogen, which is a non metal. All other nonmetals are on the right side.
The non metals have varied properties, but they do not exhibit those which characterize a metal. There are also elements that have properties of both they are called metalloids or semimetals.
The metalloids boron, silicon, germanium, arsenic, antimony, tellurium and polonium from diagonal in the periodic table; they are separate the metals from the non metals.
-AUBREY CASAJE
The periodic table is a tabular arrangement of the chemical elements, organized on the basis of their atomic numbers,electron configurations (electron shell model), and recurring chemical properties. Elements are presented in order of increasing atomic number (the number of protons in the nucleus). The standard form of the table consists of a grid of elements laid out in 18 columns and 7 rows, with a double row of elements below that. The table can also be deconstructed into four rectangular blocks: the s-block to the left, the p-block to the right, the d-block in the middle, and the f-block below that.
The rows of the table are called periods; the columns are called groups, with some of these having names such as halogensor noble gases. Since, by definition, a periodic table incorporates recurring trends, any such table can be used to derive relationships between the properties of the elements and predict the properties of new, yet to be discovered or synthesized, elements. As a result, a periodic table—whether in the standard form or some other variant—provides a useful framework for analyzing chemical behavior, and such tables are widely used in chemistry and other sciences.
Although precursors exist, Dmitri Mendeleev is generally credited with the publication, in 1869, of the first widely recognized periodic table. He developed his table to illustrate periodic trends in the properties of the then-known elements. Mendeleev also predicted some properties of then-unknown elements that would be expected to fill gaps in this table. Most of his predictions were proved correct when the elements in question were subsequently discovered. Mendeleev's periodic table has since been expanded and refined with the discovery or synthesis of further new elements and the development of new theoretical models to explain chemical behavior.
All elements from atomic numbers 1 (hydrogen) to 118 (ununoctium) have been discovered or reportedly synthesized, with elements 113, 115, 117 and 118 having yet to be confirmed. The first 98 elements exist naturally although some[n 1] are found only in trace amounts and were initially discovered by synthesis in laboratories. Elements with atomic numbers from 99 to 118 have only been synthesized, or claimed to be so, in laboratories. Production of elements having higher atomic numbers is being pursued, with the question of how the periodic table may need to be modified to accommodate any such additions being a matter of ongoing debate. Numerous synthetic radionuclides of naturally occurring elements have also been produced in laboratories.
All versions of the periodic table include only chemical elements, not mixtures, compounds, or subatomic particles.[n 2] Each chemical element has a unique atomic number representing the number of protons in its nucleus. Most elements have differing numbers of neutrons among different atoms, with these variants being referred to as isotopes. For example, carbon has three naturally occurring isotopes: all of its atoms have six protons and most have six neutrons as well, but about one per cent have seven neutrons, and a very small fraction have eight neutrons. Isotopes are never separated in the periodic table; they are always grouped together under a single element. Elements with no stable isotopes have the atomic masses of their most stable isotopes, where such masses are shown, listed in parentheses.[1]
In the standard periodic table, the elements are listed in order of increasing atomic number (the number of protons in the nucleus of an atom). A new row (period) is started when a new electron shell has its first electron. Columns (groups) are determined by the electron configuration of the atom; elements with the same number of electrons in a particular subshell fall into the same columns (e.g. oxygen and selenium are in the same column because they both have four electrons in the outermost p-subshell). Elements with similar chemical properties generally fall into the same group in the periodic table, although in the f-block, and to some respect in the d-block, the elements in the same period tend to have similar properties, as well. Thus, it is relatively easy to predict the chemical properties of an element if one knows the properties of the elements around it.[2]
As of 2013, the periodic table has 114 confirmed elements, comprising elements 1 (hydrogen) to 112 (copernicium), 114 (flerovium) and 116 (livermorium). Elements 113, 115, 117 and 118 have reportedly been synthesised in laboratories however none of these claims have been officially confirmed by the International Union of Pure and Applied Chemistry (IUPAC). As such these elements are currently known only by their systematic element names, based on their atomic numbers.[3]
A total of 98 elements occur naturally; the remaining 16 elements, from einsteinium to copernicium, and flerovium and livermorium, occur only when synthesised in laboratories. Of the 98 elements that occur naturally, 84 are primordial. The other 14 elements occur only in decay chains of primordial elements.[4] No element heavier than einsteinium (element 99) has ever been observed in macroscopic quantities in its pure form.[5]
SOURCE:http://en.wikipedia.org/wiki/Periodic_table
-ERICA BABASA
The rows of the table are called periods; the columns are called groups, with some of these having names such as halogensor noble gases. Since, by definition, a periodic table incorporates recurring trends, any such table can be used to derive relationships between the properties of the elements and predict the properties of new, yet to be discovered or synthesized, elements. As a result, a periodic table—whether in the standard form or some other variant—provides a useful framework for analyzing chemical behavior, and such tables are widely used in chemistry and other sciences.
Although precursors exist, Dmitri Mendeleev is generally credited with the publication, in 1869, of the first widely recognized periodic table. He developed his table to illustrate periodic trends in the properties of the then-known elements. Mendeleev also predicted some properties of then-unknown elements that would be expected to fill gaps in this table. Most of his predictions were proved correct when the elements in question were subsequently discovered. Mendeleev's periodic table has since been expanded and refined with the discovery or synthesis of further new elements and the development of new theoretical models to explain chemical behavior.
All elements from atomic numbers 1 (hydrogen) to 118 (ununoctium) have been discovered or reportedly synthesized, with elements 113, 115, 117 and 118 having yet to be confirmed. The first 98 elements exist naturally although some[n 1] are found only in trace amounts and were initially discovered by synthesis in laboratories. Elements with atomic numbers from 99 to 118 have only been synthesized, or claimed to be so, in laboratories. Production of elements having higher atomic numbers is being pursued, with the question of how the periodic table may need to be modified to accommodate any such additions being a matter of ongoing debate. Numerous synthetic radionuclides of naturally occurring elements have also been produced in laboratories.
All versions of the periodic table include only chemical elements, not mixtures, compounds, or subatomic particles.[n 2] Each chemical element has a unique atomic number representing the number of protons in its nucleus. Most elements have differing numbers of neutrons among different atoms, with these variants being referred to as isotopes. For example, carbon has three naturally occurring isotopes: all of its atoms have six protons and most have six neutrons as well, but about one per cent have seven neutrons, and a very small fraction have eight neutrons. Isotopes are never separated in the periodic table; they are always grouped together under a single element. Elements with no stable isotopes have the atomic masses of their most stable isotopes, where such masses are shown, listed in parentheses.[1]
In the standard periodic table, the elements are listed in order of increasing atomic number (the number of protons in the nucleus of an atom). A new row (period) is started when a new electron shell has its first electron. Columns (groups) are determined by the electron configuration of the atom; elements with the same number of electrons in a particular subshell fall into the same columns (e.g. oxygen and selenium are in the same column because they both have four electrons in the outermost p-subshell). Elements with similar chemical properties generally fall into the same group in the periodic table, although in the f-block, and to some respect in the d-block, the elements in the same period tend to have similar properties, as well. Thus, it is relatively easy to predict the chemical properties of an element if one knows the properties of the elements around it.[2]
As of 2013, the periodic table has 114 confirmed elements, comprising elements 1 (hydrogen) to 112 (copernicium), 114 (flerovium) and 116 (livermorium). Elements 113, 115, 117 and 118 have reportedly been synthesised in laboratories however none of these claims have been officially confirmed by the International Union of Pure and Applied Chemistry (IUPAC). As such these elements are currently known only by their systematic element names, based on their atomic numbers.[3]
A total of 98 elements occur naturally; the remaining 16 elements, from einsteinium to copernicium, and flerovium and livermorium, occur only when synthesised in laboratories. Of the 98 elements that occur naturally, 84 are primordial. The other 14 elements occur only in decay chains of primordial elements.[4] No element heavier than einsteinium (element 99) has ever been observed in macroscopic quantities in its pure form.[5]
SOURCE:http://en.wikipedia.org/wiki/Periodic_table
-ERICA BABASA
PERIODIC TABLE (NITROGEN)
I. Article
What is Nitrogen?
Nitrogen, symbol N, is the chemical element of atomic number 7. At room temperature, it is a gas of diatomic molecules and is colorless and odorless. Nitrogen is a common element in the universe, estimated at about seventh in total abundance in our galaxyand the Solar System. On Earth, the element is primarily found as the free element; it forms about 80% of the Earth's atmosphere. The element nitrogen was discovered as a separable component of air by Scottish physician Daniel Rutherford in 1772. Many industrially important compounds, such as ammonia, nitric acid, organic nitrates (propellants and explosives), and cyanides, contain nitrogen. The extremely strong bond in elemental nitrogen dominates nitrogen chemistry, causing difficulty for both organisms and industry in converting the N2 into useful compounds, but at the same time causing release of large amounts of often useful energy when the compounds burn, explode, or decay back into nitrogen gas. Synthetically-produced ammonia and nitrates are key industrial fertilizers and fertilizer nitrates are key pollutants in causing the eutrophication of water systems.
Outside their major uses as fertilizers and energy-stores, nitrogen compounds are versatile organics. Nitrogen is part of materials as diverse as Kevlar fabric and cyanoacrylate "super" glue. Nitrogen is a constituent of molecules in every major pharmacological drug class, including the antibiotics. Many drugs are mimics or prodrugs of natural nitrogen-containing signal molecules: for example, the organic nitrates nitroglycerin and nitroprusside control blood pressure by being metabolized to natural nitric oxide. Plant alkaloids(often defense chemicals) contain nitrogen by definition, and thus many notable nitrogen-containing drugs, such as caffeine andmorphine are either alkaloids or synthetic mimics that act (as many plant alkaloids do) upon receptors of animal neurotransmitters(for example, synthetic amphetamines).
Nitrogen occurs in all organisms, primarily in amino acids (and thus proteins) and also in the nucleic acids (DNA and RNA). The human body contains about 3% by weight of nitrogen, the fourth most abundant element in the body after oxygen, carbon, and hydrogen. The nitrogen cycle describes movement of the element from the air, into the biosphere and organic compounds, then back into the atmosphere.
Source: http://en.wikipedia.org/wiki/Nitrogen
II. News
Nitrogen pollution soars in China
Emissions from transport and industry have increased faster than those from agriculture.
-Jane Qiu
Nitrogen-containing pollutants from agriculture, transport and industry in China has increased by more than half in 30 years, a study shows, adding to concerns about the country’s deteriorating environment.
“Rapid economic growth in China has driven high levels of nitrogen emissions in the past few decades,” says Zhang Fusuo, an agriculture researcher at the China Agricultural University in Beijing and a co-author of the study.
Once emitted into the air, key nitrogen pollutants — ammonia and nitrogen oxides — can be transformed to secondary pollutants such as ammonium and nitrates, and then washed to Earth by rain and snow. The process, known as nitrogen deposition, can do great damage to ecosystems, causing soil acidification, fertilizing harmful algal blooms and threatening biodiversity, says Zhang. But until his study, “there was little direct evidence for the magnitude of the problem in China”.
By analysing data from 270 monitoring sites around the country, Zhang and his colleagues found that the amount of nitrogen deposition, as measured in precipitation, had increased by 60% — or 8 kilograms per hectare per year — between 1980 and 2010. The study is published in Nature today1.
The researchers went on to assess how this had affected ecosystems. They found that the leaves of a range of herbaceous and woody plants across China were absorbing 33% more nitrogen than in 1980. Similarly, nitrogen uptake by rice, wheat and maize (corn) on long-term unfertilized farmland had increased by about 16% in the same period.
“This is the first major analysis of nitrogen deposition in China,” says Mark Sutton, an environmental scientist at the Centre for Ecology and Hydrology in Edinburgh, UK. “The scale of the study is impressive. It allows the statistical power to detect changes and trends.”
Transport accelerates
“The composition of nitrogen deposition has changed over the years,” says Zhang. In 2010, about one-third of deposited nitrogen was in the form of nitrate, with the rest being ammonium; by contrast, in 1980, nitrate made up just 17% of deposited nitrogen. This suggests, he says, that nitrogen oxide emissions from transport and industry are increasing more rapidly than ammonia emissions from agriculture.
“This is consistent with the growth of those sectors,” says Zhang. Since the 1980s, the use of nitrogen fertilizers and the number of livestock have doubled, whereas coal consumption has increased more than 3-fold and the number of motor vehicles more than 20-fold.
If the current trends persist, ammonia emissions will increase by 85% by 2050; nitrogen oxide emissions will go up more than eightfold. “The impact will be unthinkable,” says Zhang.
Global trouble
Sutton, who co-authored a commentary2 published alongside Zhang's article, points out that nitrogen is not just a Chinese problem. Globally each year, around 140 million tonnes of nitrogen is lost to the environment as ammonia, nitrogen oxides and other compounds. That figure is projected to increase by 70% by 2050 — when emerging economies in Latin America and South Asia are likely to have the same nitrogen pollution problems as China.
This “is exacerbating climate change and having a whole range of effects on the environment and public health,” says Sutton. According to a report commissioned by the United Nations Environment Programme (UNEP) and launched on 18 February by the Global Partnership on Nutrient Management and International Nitrogen Initiative, nitrogen pollution causes US$200-US$2,000 billion of damage around the world each year3.
“It’s time to curb global nitrogen pollution,” says Sutton, who led the UNEP study. Improving practices in agriculture — the biggest contributor of nitrogen pollution worldwide — should be a top priority, he says.
“Fertilizer overuse is a common problem, especially in developing countries,” agrees Zhang. In an earlier study4, he and his colleagues found that Chinese farmers use an average of around 600 kilograms of nitrogen fertilizers per hectare per year, but that could be cut by up to two-thirds without affecting crop yields.
Furthermore, says Sutton, “80% of the nitrogen in crops grown globally goes to feed livestock,” says Sutton. Higher consumption of meat and diary products, especially in developed countries, has substantially increased global nitrogen pollution. “Recycling nitrogen from manure and sewage would increase the efficiency of nutrient use, while reducing pollution and improving crop production.”
To make a real difference, he adds, “governments should join forces to better manage the global nitrogen cycle.”
Source: http://www.nature.com/news/nitrogen-pollution-soars-in-china-1.12470
© 2014 Nature Publishing Group, a division of Macmillan Publishers Limited. All Rights Reserved.partner of AGORA, HINARI, OARE, INASP, CrossRef and COUNTER
III. Experiment
Experimental study on Nitrogen components during composting process of feces We measured nitrogen components during composting process of feces in a batch test in which sawdust was used as a matrix. Further decomposition rates of fecal nitrogen and carbon were obtained in the batch tests of different feces loading. In composting material that was a mixture of sawdust and fresh feces, fecal organic matter decomposed to CO2 and fecal nitrogen mineralized to ammonia during the composting process. The biological response of organic matter and nitrogen in the composting material was evaluated by oxygen consumption (OUR) and ammonia production that was a sum of volatilized ammonia gas and ammonia remaining in the composting material. Since composting material contains two different sources of organic matter from feces and sawdust, the OUR by using the sawdust matrix only was evaluated in preliminary tests. The fecal contribution to the OUR in the composting material was therefore calculated by subtraction of the result in the preliminary tests from the one in the composting material. The ammonia production from the fecal nitrogen was obtained by the same procedure. The decomposition rates of input organic matter in feces were approximately 83 and 70% respectively, whereas ammonia production rates were approximately 73 and 58% of input fecal nitrogen. There was an interesting time lag of the peak time between volatilisation rates of ammonia and CO2 during the composting process while fecal carbon and nitrogen simultaneously decomposed to ammonia and CO2 in the composting material.
Source: http://www.ncbi.nlm.nih.gov/pubmed/17506436
National Center for Biotechnology Information, U.S. National Library of Medicine8600 Rockville Pike, Bethesda MD, 20894 USA
-THERESA ABILLAR
I. Article
What is Nitrogen?
Nitrogen, symbol N, is the chemical element of atomic number 7. At room temperature, it is a gas of diatomic molecules and is colorless and odorless. Nitrogen is a common element in the universe, estimated at about seventh in total abundance in our galaxyand the Solar System. On Earth, the element is primarily found as the free element; it forms about 80% of the Earth's atmosphere. The element nitrogen was discovered as a separable component of air by Scottish physician Daniel Rutherford in 1772. Many industrially important compounds, such as ammonia, nitric acid, organic nitrates (propellants and explosives), and cyanides, contain nitrogen. The extremely strong bond in elemental nitrogen dominates nitrogen chemistry, causing difficulty for both organisms and industry in converting the N2 into useful compounds, but at the same time causing release of large amounts of often useful energy when the compounds burn, explode, or decay back into nitrogen gas. Synthetically-produced ammonia and nitrates are key industrial fertilizers and fertilizer nitrates are key pollutants in causing the eutrophication of water systems.
Outside their major uses as fertilizers and energy-stores, nitrogen compounds are versatile organics. Nitrogen is part of materials as diverse as Kevlar fabric and cyanoacrylate "super" glue. Nitrogen is a constituent of molecules in every major pharmacological drug class, including the antibiotics. Many drugs are mimics or prodrugs of natural nitrogen-containing signal molecules: for example, the organic nitrates nitroglycerin and nitroprusside control blood pressure by being metabolized to natural nitric oxide. Plant alkaloids(often defense chemicals) contain nitrogen by definition, and thus many notable nitrogen-containing drugs, such as caffeine andmorphine are either alkaloids or synthetic mimics that act (as many plant alkaloids do) upon receptors of animal neurotransmitters(for example, synthetic amphetamines).
Nitrogen occurs in all organisms, primarily in amino acids (and thus proteins) and also in the nucleic acids (DNA and RNA). The human body contains about 3% by weight of nitrogen, the fourth most abundant element in the body after oxygen, carbon, and hydrogen. The nitrogen cycle describes movement of the element from the air, into the biosphere and organic compounds, then back into the atmosphere.
Source: http://en.wikipedia.org/wiki/Nitrogen
II. News
Nitrogen pollution soars in China
Emissions from transport and industry have increased faster than those from agriculture.
-Jane Qiu
Nitrogen-containing pollutants from agriculture, transport and industry in China has increased by more than half in 30 years, a study shows, adding to concerns about the country’s deteriorating environment.
“Rapid economic growth in China has driven high levels of nitrogen emissions in the past few decades,” says Zhang Fusuo, an agriculture researcher at the China Agricultural University in Beijing and a co-author of the study.
Once emitted into the air, key nitrogen pollutants — ammonia and nitrogen oxides — can be transformed to secondary pollutants such as ammonium and nitrates, and then washed to Earth by rain and snow. The process, known as nitrogen deposition, can do great damage to ecosystems, causing soil acidification, fertilizing harmful algal blooms and threatening biodiversity, says Zhang. But until his study, “there was little direct evidence for the magnitude of the problem in China”.
By analysing data from 270 monitoring sites around the country, Zhang and his colleagues found that the amount of nitrogen deposition, as measured in precipitation, had increased by 60% — or 8 kilograms per hectare per year — between 1980 and 2010. The study is published in Nature today1.
The researchers went on to assess how this had affected ecosystems. They found that the leaves of a range of herbaceous and woody plants across China were absorbing 33% more nitrogen than in 1980. Similarly, nitrogen uptake by rice, wheat and maize (corn) on long-term unfertilized farmland had increased by about 16% in the same period.
“This is the first major analysis of nitrogen deposition in China,” says Mark Sutton, an environmental scientist at the Centre for Ecology and Hydrology in Edinburgh, UK. “The scale of the study is impressive. It allows the statistical power to detect changes and trends.”
Transport accelerates
“The composition of nitrogen deposition has changed over the years,” says Zhang. In 2010, about one-third of deposited nitrogen was in the form of nitrate, with the rest being ammonium; by contrast, in 1980, nitrate made up just 17% of deposited nitrogen. This suggests, he says, that nitrogen oxide emissions from transport and industry are increasing more rapidly than ammonia emissions from agriculture.
“This is consistent with the growth of those sectors,” says Zhang. Since the 1980s, the use of nitrogen fertilizers and the number of livestock have doubled, whereas coal consumption has increased more than 3-fold and the number of motor vehicles more than 20-fold.
If the current trends persist, ammonia emissions will increase by 85% by 2050; nitrogen oxide emissions will go up more than eightfold. “The impact will be unthinkable,” says Zhang.
Global trouble
Sutton, who co-authored a commentary2 published alongside Zhang's article, points out that nitrogen is not just a Chinese problem. Globally each year, around 140 million tonnes of nitrogen is lost to the environment as ammonia, nitrogen oxides and other compounds. That figure is projected to increase by 70% by 2050 — when emerging economies in Latin America and South Asia are likely to have the same nitrogen pollution problems as China.
This “is exacerbating climate change and having a whole range of effects on the environment and public health,” says Sutton. According to a report commissioned by the United Nations Environment Programme (UNEP) and launched on 18 February by the Global Partnership on Nutrient Management and International Nitrogen Initiative, nitrogen pollution causes US$200-US$2,000 billion of damage around the world each year3.
“It’s time to curb global nitrogen pollution,” says Sutton, who led the UNEP study. Improving practices in agriculture — the biggest contributor of nitrogen pollution worldwide — should be a top priority, he says.
“Fertilizer overuse is a common problem, especially in developing countries,” agrees Zhang. In an earlier study4, he and his colleagues found that Chinese farmers use an average of around 600 kilograms of nitrogen fertilizers per hectare per year, but that could be cut by up to two-thirds without affecting crop yields.
Furthermore, says Sutton, “80% of the nitrogen in crops grown globally goes to feed livestock,” says Sutton. Higher consumption of meat and diary products, especially in developed countries, has substantially increased global nitrogen pollution. “Recycling nitrogen from manure and sewage would increase the efficiency of nutrient use, while reducing pollution and improving crop production.”
To make a real difference, he adds, “governments should join forces to better manage the global nitrogen cycle.”
Source: http://www.nature.com/news/nitrogen-pollution-soars-in-china-1.12470
© 2014 Nature Publishing Group, a division of Macmillan Publishers Limited. All Rights Reserved.partner of AGORA, HINARI, OARE, INASP, CrossRef and COUNTER
III. Experiment
Experimental study on Nitrogen components during composting process of feces We measured nitrogen components during composting process of feces in a batch test in which sawdust was used as a matrix. Further decomposition rates of fecal nitrogen and carbon were obtained in the batch tests of different feces loading. In composting material that was a mixture of sawdust and fresh feces, fecal organic matter decomposed to CO2 and fecal nitrogen mineralized to ammonia during the composting process. The biological response of organic matter and nitrogen in the composting material was evaluated by oxygen consumption (OUR) and ammonia production that was a sum of volatilized ammonia gas and ammonia remaining in the composting material. Since composting material contains two different sources of organic matter from feces and sawdust, the OUR by using the sawdust matrix only was evaluated in preliminary tests. The fecal contribution to the OUR in the composting material was therefore calculated by subtraction of the result in the preliminary tests from the one in the composting material. The ammonia production from the fecal nitrogen was obtained by the same procedure. The decomposition rates of input organic matter in feces were approximately 83 and 70% respectively, whereas ammonia production rates were approximately 73 and 58% of input fecal nitrogen. There was an interesting time lag of the peak time between volatilisation rates of ammonia and CO2 during the composting process while fecal carbon and nitrogen simultaneously decomposed to ammonia and CO2 in the composting material.
Source: http://www.ncbi.nlm.nih.gov/pubmed/17506436
National Center for Biotechnology Information, U.S. National Library of Medicine8600 Rockville Pike, Bethesda MD, 20894 USA
-THERESA ABILLAR
The alkali metals are a group in the periodic table consisting of the chemical elements lithium (Li), sodium(Na), potassium (K), rubidium (Rb), caesium (Cs), and francium (Fr). This group lies in the s-block of the periodic tableas all alkali metals have their outermost electron in an s-orbital. The alkali metals provide the best example of group trends in properties in the periodic table, with elements exhibiting well-characterized homologous behavior.[
The alkali metals have very similar properties: they are all shiny, soft, highly reactive metals at standard temperature and pressure and readily lose their outermost electron to form cations with charge +1. They can all be cut easily with a knife due to their softness, exposing a shiny surface that tarnishes rapidly in air due to oxidation. Because of their high reactivity, they must be stored under oil to prevent reaction with air,] and are found naturally only in salts and never as the free element. In the modern IUPAC nomenclature, the alkali metals comprise the group 1 elements, excluding hydrogen (H), which is nominally a group 1 element but not normally considered to be an alkali metal. as it rarely exhibits behavior comparable to that of the alkali metals. All the alkali metals react with water, with the heavier alkali metals reacting more vigorously than the lighter ones.
All the discovered alkali metals occur in nature: in order of abundance, sodium is the most abundant, followed by potassium, lithium, rubidium, caesium, and finally francium, which is very rare due to its extremely high radioactivity and thus occurs only in traces due to its presence in natural decay chains. Experiments have been conducted to attempt the synthesis of ununennium (Uue), which is likely to be the next member of the group, but they have all met with failure. However, ununennium may not be an alkali metal due to relativistic effects, which are predicted to have a large influence on the chemical properties of super heavy elements; even if it does turn out to be an alkali metal, it is predicted to have some differences in physical and chemical properties from its lighter homologues.
Most alkali metals have many different applications. Two of the most well-known applications of the pure elements are rubidium and caesium atomic clocks, of which caesium atomic clocks are the most accurate and precise representation of time. A common application of the compounds of sodium is the sodium-vapor lamp, which emits very efficient light. Table salt, or sodium chloride, has been used since antiquity. Sodium and potassium are also essential elements, having major biological roles as electrolytes, and although the other alkali metals are not essential, they also have various effects on the body, both beneficial and harmful.
Source from: http://en.wikipedia.org/wiki/Alkali_metal
-KIZEL MOSQUEDA
-JASTINE NICDAO
The alkali metals have very similar properties: they are all shiny, soft, highly reactive metals at standard temperature and pressure and readily lose their outermost electron to form cations with charge +1. They can all be cut easily with a knife due to their softness, exposing a shiny surface that tarnishes rapidly in air due to oxidation. Because of their high reactivity, they must be stored under oil to prevent reaction with air,] and are found naturally only in salts and never as the free element. In the modern IUPAC nomenclature, the alkali metals comprise the group 1 elements, excluding hydrogen (H), which is nominally a group 1 element but not normally considered to be an alkali metal. as it rarely exhibits behavior comparable to that of the alkali metals. All the alkali metals react with water, with the heavier alkali metals reacting more vigorously than the lighter ones.
All the discovered alkali metals occur in nature: in order of abundance, sodium is the most abundant, followed by potassium, lithium, rubidium, caesium, and finally francium, which is very rare due to its extremely high radioactivity and thus occurs only in traces due to its presence in natural decay chains. Experiments have been conducted to attempt the synthesis of ununennium (Uue), which is likely to be the next member of the group, but they have all met with failure. However, ununennium may not be an alkali metal due to relativistic effects, which are predicted to have a large influence on the chemical properties of super heavy elements; even if it does turn out to be an alkali metal, it is predicted to have some differences in physical and chemical properties from its lighter homologues.
Most alkali metals have many different applications. Two of the most well-known applications of the pure elements are rubidium and caesium atomic clocks, of which caesium atomic clocks are the most accurate and precise representation of time. A common application of the compounds of sodium is the sodium-vapor lamp, which emits very efficient light. Table salt, or sodium chloride, has been used since antiquity. Sodium and potassium are also essential elements, having major biological roles as electrolytes, and although the other alkali metals are not essential, they also have various effects on the body, both beneficial and harmful.
Source from: http://en.wikipedia.org/wiki/Alkali_metal
-KIZEL MOSQUEDA
-JASTINE NICDAO
Metals, Metalloids, and Nonmetals
The elements can be classified as metals, nonmetals, or metalloids. Metals are good conductors of heat and electricity, and are malleable (they can be hammered into sheets) and ductile (they can be drawn into wire). Most of the metals are solids at room temperature, with a characteristic silvery shine (except for mercury, which is a liquid). Nonmetals are (usually) poor conductors of heat and electricity, and are not malleable or ductile; many of the elemental nonmetals are gases at room temperature, while others are liquids and others are solids. The metalloids are intermediate in their properties. In their physical properties, they are more like the nonmetals, but under certain circumstances, several of them can be made to conduct electricity. These semiconductors are extremely important in computers and other electronic devices.
On many periodic tables, a jagged black line (see figure below) along the right side of the table separates the metals from the nonmetals. The metals are to the left of the line (except for hydrogen, which is a nonmetal), the nonmetals are to the right of the line, and the elements immediately adjacent to the line are the metalloids.
When elements combine to form compounds, there are two major types of bonding that can result. Ionic bonds form when there is a transfer of electrons from one species to another, producing charged ions which attract each other very strongly by electrostatic interactions, and covalent bonds, which result when atoms share electrons to produce neutral molecules. In general, metal and nonmetals combine to form ionic compounds, while nonmetals combine with other nonmetals to form covalent compounds (molecules).
Since the metals are further to the left on the periodic table, they have low ionization energies and low electron affinities, so they lose electrons relatively easily and gain them with difficulty. They also have relatively few valence electrons, and can form ions (and thereby satisfy the octet rule) more easily by losing their valence electrons to form positively charged cations.
The main-group metals usually form charges that are the same as their group number: that is, the Group 1A metals such as sodium and potassium form +1 charges, the Group 2A metals such as magnesium and calcium form 2+ charges, and the Group 3A metals such as aluminum form 3+ charges.
The metals which follow the transition metals (towards the bottom of Groups 4A and 5A) can lose either their outermost s and p electrons, forming charges that are identical to their group number, or they can lose just the p electrons while retaining their two s electrons, forming charges that are the group number minus two. In other words, tin and lead in Group 4A can form either 4+ or 2+ charges, while bismuth in Group 5A can form either a 5+ or a 3+ charge.
The transition metals usually are capable of forming 2+ charges by losing their valence s electrons, but can also lose electrons from their d orbitals to form other charges. Most of the transition metals can form more than one possible charge in ionic compounds.
Nonmetals are further to the right on the periodic table, and have high ionization energies and high electron affinities, so they gain electrons relatively easily, and lose them with difficulty. They also have a larger number of valence electrons, and are already close to having a complete octet of eight electrons. The nonmetals gain electrons until they have the same number of electrons as the nearest noble gas (Group 8A), forming negatively charged anions which have charges that are the group number minus eight. That is, the Group 7A nonmetals form 1- charges, the Group 6A nonmetals form 2- charges, and the Group 5A metals form 3- charges. The Group 8A elements already have eight electrons in their valence shells, and have little tendency to either gain or lose electrons, and do not readily form ionic or molecular compounds.
Ionic compounds are held together in a regular array called a crystal lattice by the attractive forces between the oppositely charged cations and anions. These attractive forces are very strong, and most ionic compounds therefore have very high melting points. (For instance, sodium chloride, NaCl, melts at 801°C, while aluminum oxide, Al2O3, melts at 2054°C.) Ionic compounds are typically hard, rigid, and brittle. Ionic compounds do not conduct electricity, because the ions are not free to move in the solid phase, but ionic compounds can conduct electricity when they are dissolved in water.
When nonmetals combine with other nonmetals, they tend to share electrons in covalent bonds instead of forming ions, resulting in the formation of neutral molecules. (Keep in mind that since hydrogen is also a nonmetal, the combination of hydrogen with another nonmetal will also produce a covalent bond.) Molecular compounds can be gases, liquids, or low melting point solids, and comprise a wide variety of substances. (See the Molecule Gallery for examples.)
When metals combine with each other, the bonding is usually described as metallic bonding (you could've guessed that). In this model, each metal atom donates one or more of its valence electrons to make an electron sea that surrounds all of the atoms, holding the substance together by the attraction between the metal cations and the negatively charged electrons. Since the electrons in the electron sea can move freely, metals conduct electricity very easily, unlike molecules, where the electrons are more localized. Metal atoms can move past each other more easily than those in ionic compounds (which are held in fixed positions by the attractions between cations and anions), allowing the metal to be hammered into sheets or drawn into wire. Different metals can be combined very easily to make alloys, which can have much different physical properties from their constituent metals. Steel is an alloy of iron and carbon, which is much harder than iron itself; chromium, vanadium, nickel, and other metals are also often added to iron to make steels of various types. Brass is an alloy of copper and zinc which is used in plumbing fixtures, electrical parts, and musical instruments. Bronze is an alloy of copper and tin, which is much harder than copper; when bronze was discovered by ancient civilizations, it marked a significant step forward from the use of less durable stone tools.
Source from: http://www.angelo.edu/faculty/kboudrea/periodic/physical_metals.htm
-Carmela Viray
The elements can be classified as metals, nonmetals, or metalloids. Metals are good conductors of heat and electricity, and are malleable (they can be hammered into sheets) and ductile (they can be drawn into wire). Most of the metals are solids at room temperature, with a characteristic silvery shine (except for mercury, which is a liquid). Nonmetals are (usually) poor conductors of heat and electricity, and are not malleable or ductile; many of the elemental nonmetals are gases at room temperature, while others are liquids and others are solids. The metalloids are intermediate in their properties. In their physical properties, they are more like the nonmetals, but under certain circumstances, several of them can be made to conduct electricity. These semiconductors are extremely important in computers and other electronic devices.
On many periodic tables, a jagged black line (see figure below) along the right side of the table separates the metals from the nonmetals. The metals are to the left of the line (except for hydrogen, which is a nonmetal), the nonmetals are to the right of the line, and the elements immediately adjacent to the line are the metalloids.
When elements combine to form compounds, there are two major types of bonding that can result. Ionic bonds form when there is a transfer of electrons from one species to another, producing charged ions which attract each other very strongly by electrostatic interactions, and covalent bonds, which result when atoms share electrons to produce neutral molecules. In general, metal and nonmetals combine to form ionic compounds, while nonmetals combine with other nonmetals to form covalent compounds (molecules).
Since the metals are further to the left on the periodic table, they have low ionization energies and low electron affinities, so they lose electrons relatively easily and gain them with difficulty. They also have relatively few valence electrons, and can form ions (and thereby satisfy the octet rule) more easily by losing their valence electrons to form positively charged cations.
The main-group metals usually form charges that are the same as their group number: that is, the Group 1A metals such as sodium and potassium form +1 charges, the Group 2A metals such as magnesium and calcium form 2+ charges, and the Group 3A metals such as aluminum form 3+ charges.
The metals which follow the transition metals (towards the bottom of Groups 4A and 5A) can lose either their outermost s and p electrons, forming charges that are identical to their group number, or they can lose just the p electrons while retaining their two s electrons, forming charges that are the group number minus two. In other words, tin and lead in Group 4A can form either 4+ or 2+ charges, while bismuth in Group 5A can form either a 5+ or a 3+ charge.
The transition metals usually are capable of forming 2+ charges by losing their valence s electrons, but can also lose electrons from their d orbitals to form other charges. Most of the transition metals can form more than one possible charge in ionic compounds.
Nonmetals are further to the right on the periodic table, and have high ionization energies and high electron affinities, so they gain electrons relatively easily, and lose them with difficulty. They also have a larger number of valence electrons, and are already close to having a complete octet of eight electrons. The nonmetals gain electrons until they have the same number of electrons as the nearest noble gas (Group 8A), forming negatively charged anions which have charges that are the group number minus eight. That is, the Group 7A nonmetals form 1- charges, the Group 6A nonmetals form 2- charges, and the Group 5A metals form 3- charges. The Group 8A elements already have eight electrons in their valence shells, and have little tendency to either gain or lose electrons, and do not readily form ionic or molecular compounds.
Ionic compounds are held together in a regular array called a crystal lattice by the attractive forces between the oppositely charged cations and anions. These attractive forces are very strong, and most ionic compounds therefore have very high melting points. (For instance, sodium chloride, NaCl, melts at 801°C, while aluminum oxide, Al2O3, melts at 2054°C.) Ionic compounds are typically hard, rigid, and brittle. Ionic compounds do not conduct electricity, because the ions are not free to move in the solid phase, but ionic compounds can conduct electricity when they are dissolved in water.
When nonmetals combine with other nonmetals, they tend to share electrons in covalent bonds instead of forming ions, resulting in the formation of neutral molecules. (Keep in mind that since hydrogen is also a nonmetal, the combination of hydrogen with another nonmetal will also produce a covalent bond.) Molecular compounds can be gases, liquids, or low melting point solids, and comprise a wide variety of substances. (See the Molecule Gallery for examples.)
When metals combine with each other, the bonding is usually described as metallic bonding (you could've guessed that). In this model, each metal atom donates one or more of its valence electrons to make an electron sea that surrounds all of the atoms, holding the substance together by the attraction between the metal cations and the negatively charged electrons. Since the electrons in the electron sea can move freely, metals conduct electricity very easily, unlike molecules, where the electrons are more localized. Metal atoms can move past each other more easily than those in ionic compounds (which are held in fixed positions by the attractions between cations and anions), allowing the metal to be hammered into sheets or drawn into wire. Different metals can be combined very easily to make alloys, which can have much different physical properties from their constituent metals. Steel is an alloy of iron and carbon, which is much harder than iron itself; chromium, vanadium, nickel, and other metals are also often added to iron to make steels of various types. Brass is an alloy of copper and zinc which is used in plumbing fixtures, electrical parts, and musical instruments. Bronze is an alloy of copper and tin, which is much harder than copper; when bronze was discovered by ancient civilizations, it marked a significant step forward from the use of less durable stone tools.
Source from: http://www.angelo.edu/faculty/kboudrea/periodic/physical_metals.htm
-Carmela Viray