Purdue carbon dating
The Chemistry of Nonmetals The Chemistry of Hydrogen The Chemistry of Oxygen and Sulfur The Chemistry of Nitrogen and Phosphorous The Chemistry of the Halogens The Chemistry of the Rare Gases The Inorganic Chemistry of Carbon), that contain both carbon and hydrogen.The chemistry of carbon is dominated by three factors. Carbon forms unusually strong C-C single bonds, C=C double bonds, and carbon-carbon triple bonds. The electronegativity of carbon ( ions when it reacts with nonmetals.Carbon therefore forms covalent bonds with many other elements. Carbon forms strong double and triple bonds with a number of other nonmetals, including N, O, P, and S. There are two crystalline forms diamond and graphiteand a number of amorphous (noncrystalline) forms, such as charcoal, coke, and carbon black.References to the characteristic hardness of diamond (from the Greek , "invincible") date back at least 2600 years.It was not until 1797, however, that Smithson Tennant was able to show that diamonds consist solely of carbon. It is among the least volatile substances known (C), it is also the hardest substance known, and it expands less on heating than any other material.
The strength of the individual C-C bonds and their arrangement in space give rise to the unusual properties of diamond.In some ways, the properties of graphite are like those of diamond. Whereas diamond is the hardest substance known, graphite is one of the softest.Diamond is an excellent insulator, with little or no tendency to carry an electric current.Graphite is such a good conductor of electricity that graphite electrodes are used in electrical cells.The physical properties of graphite can be understood from the structure of the solid shown in the figure below.Graphite consists of extended planes of explain the exceptionally high melting point and boiling point of graphite.) The distance between these planes of atoms, however, is very much larger than the distance between the atoms within the planes.Because the bonds are weak, it is easy to deform the solid by allowing one plane of atoms to move relative to another.As a result, graphite is soft enough to be used in pencils and as a lubricant in motor oil. (This is fortunate because many people chew pencils and lead compounds are toxic.) Lead pencils contain graphite, or "black lead" as it was once known, which is mixed with clay (20% to 60% by weight) and then baked to form a ceramic rod.Increasing the percentage of clay makes the pencil harder, so that less graphite is deposited on the paper.The characteristic properties of graphite and diamond might lead you to expect that diamond would be more stable than graphite. The standard enthalpy of formation of diamond (C and 1 atm pressure.At very high temperatures and pressures, diamond becomes more stable than graphite.