Cost of carbon 14 dating
A large family of fullerenes exists, starting at C20 and reaching up to C540.
The most recently discovered allotrope of carbon is graphene, which consists of a single layer of carbon atoms arranged in hexagons.
Note: At normal atmospheric pressure, carbon does not melt when heated, it sublimes. it undergoes a phase change directly from solid to gas.
If the pressure is increased to 10 atmospheres carbon (graphite) is observed to melt at 3550 °C.
Interestingly, graphite is one of the softest substances and diamond was thought, until recently, to be the hardest naturally occurring substance.
An extremely rare allotrope of carbon, lonsdaleite, has been calculated, in pure form, to be 58% stronger than diamond.
Characteristics: Carbon can exist with several different 3 dimensional structures in which its atoms are arranged differently (allotropes).
Three common crystalline allotropes are graphite, diamond, and (usually) fullerenes.
The structures of eight allotropes are shown at the bottom of this page.In 1779, Swedish scientist Carl Scheele showed that graphite burned to form carbon dioxide and so must be another form of carbon.In 1796, English chemist Smithson Tennant established that diamond was pure carbon and not a compound of carbon; it burned to form only carbon dioxide.Graphite is used for pencil tips, high temperature crucibles, dry cells, electrodes and as a lubricant.Diamonds are used in jewelry and – because they are so hard – in industry for cutting, drilling, grinding, and polishing.