Carbon (6)

Given that so much can be said about this element, of which SO MANY things on our planet is comprised of...I am trying to keep this as short as possible...

Carbon is a Group 14 element and is distributed very widely in nature. It is found in abundance in the sun, stars, comets, and atmospheres of most planets.

Carbon is found free in nature in three allotropic forms: amorphous, graphite, and di...amond (further details). Graphite is one of the softest known materials while diamond is one of the hardest. Carbon, as microscopic diamonds, is found in some meteorites. Natural diamonds are found in ancient volcanic "pipes" such as found in South Africa. Diamonds are also recovered from the ocean floor off the Cape of Good Hope.

•Name: Carbon
•Symbol: C
•Atomic number: 6
•Atomic weight: 12.0107
•Standard state: solid at 298 K
•CAS Registry ID: 7440-44-0
•Group in periodic table: 14
•Group name: (none)
•Period in periodic table: 2
•Block in periodic table: p-block
•Color: graphite is black, diamond is colorless
•Classification: Non-metallic

Carbon is present as carbon dioxide in the atmosphere and dissolved in all natural waters. It is a component of rocks as carbonates of calcium (limestone), magnesium, and iron. The atmosphere of Mars contains 96 % CO2.

Coal, petroleum, and natural gas are chiefly hydrocarbons. Carbon is unique among the elements in the vast number of variety of compounds it can form. Organic chemistry, a 1/112th subset of inorganic chemistry, is the study of carbon and its compounds. While silicon might take the place of carbon in forming a host of related compounds, it is not possible currently to form stable compounds with very long chains of silicon atoms.

In 1961 the International Union of Pure and Applied Chemistry (IUPAC) adopted the isotope 12C as the basis for atomic weights. Carbon-14, 14C, an isotope with a half-life of 5730 years, is used to date such materials as wood, archeological specimens, etc. Carbon-13, 13C, is particularly useful for isotopic labelling studies since it is not radioactive, but is a spin I = 1/2 nucleus and therefore a good NMR nucleus.

Historical information

Carbon was discovered by Known since ancient times although not recognized as an element until much later. Origin of name: from the Latin word "carbo" meaning "charcoal". Carbon as charcoal, soot and coal has been used since prehistoric times. Carbon as diamond has also been known since very ancient times. The recognition that soot (amorphous carbon), graphite (another form of carbon) and diamond are all forms of carbon.

A fourth form, buckminsterfullerene, formula C60, whose framework is reminiscent of the seams in an Association Football ("soccer") ball, is the subject of considerable interest at present and was only discovered a few years ago in work involving Harry Kroto, a Sheffield graduate.

Sometime prior to the autumn of 1803, the Englishman John Dalton was able to explain the results of some of his studies by assuming that matter is composed of atoms and that all samples of any given compound consist of the same combination of these atoms. Dalton also noted that in series of compounds, the ratios of the masses of the second element that combine with a given weight of the first element can be reduced to small whole numbers (the law of multiple proportions). This was further evidence for atoms. Dalton's theory of atoms was published by Thomas Thomson in the 3rd edition of his System of Chemistry in 1807 and in a paper about strontium oxalates published in the Philosophical Transactions. Dalton published these ideas himself in the following year in the New System of Chemical Philosophy.

Physical properties

•Melting point: 3800 [or 3500 °C (6400 °F)] K
•Boiling point: 4300 [or 4027 °C (7281 °F)] K
•Density of solid: 2267 kg m-3

Orbital properties

•Ground state electron configuration: [He].2s2.2p2
•Shell structure: 2.4
•Term symbol: 3P0

Isolation

Carbon is available in nature as graphite and (to a much lesser extent!) as diamond. Artificial graphite is made by the reaction of coke with silica (SiO2).

SiO2 + 3C (2500°C) → "SiC" → Si (g) + C(graphite)

Artificial diamonds are made by the application of heat and pressure (> 125 kBar) in the presence of a catalyst such as iron, chromium or platinum. It seems that the metal melts on the carbon surface, the graphite dissolves in the metal film, and the less soluble diamond precipitates out. The introduction of nitrogen as an impurity gives yellowish diamonds while boron impurities give bluish colors.

A new form of carbon, buckminsterfullerene with formula C60 is formed in the treatment of graphite by lasers and is now commercially available in small quantities.