The different forms of carbon include the hardest naturally occurring substance, diamond, and one of the softest substances, graphite. It also bonds with other atoms fairly easily and is also capable of forming covalent bonds with other atoms. This makes carbon able to make the majority of chemical compounds with almost ten million different compounds. Carbon has the highest sublimation point (transition from solid straight to gas [2]) of all the elements. It also has no melting point at atmospheric pressure because it has a triple point (the temperature and pressure at which the solid, liquid, and gas states coexist in equilibrium [3]) at 7820 degrees Fahrenheit. This means the sublimation point is at about 3900 Kelvin.

Carbon compounds form the basics of all life on Earth. The carbon-nitrogen cycle even provides some of the energy produced by the sun. There are many forms of carbon, and many varieties, however most of them are unreactive under normal conditions. It doesn’t react with sulfuric acid, hydrochloric acid, chlorine or any alkalis. Carbon resists all most all oxidizers at normal temperatures and pressures. At higher temperatures carbon with oxygen forms carbon oxides. Carbon can combine with some metals when there is a high temperature to form metallic carbides, which are used for making harder, tips for cutting tools and is also used for abrasives.

http://en.wikipedia.org/wiki/Carbon,