Carbon
Carbon is an abundant non-metal. It is in the atmosphere as carbon dioxide, in animal and plant tissues, in every organic compound, and in coal, petroleum products and other hydrocarbons — where it is the main building unit.
Crystalline and amorphous
Carbon has crystalline forms and amorphous forms. In the crystalline forms the atoms are arranged in a definite pattern; in the amorphous forms there is no such pattern. It is the crystalline forms that show allotropy.
- Crystalline carbon — diamond, graphite, fullerene
- Amorphous carbon — charcoal, lamp black, coal
Figure to be added
Physical properties
These vary with the form. Every form except diamond is black and solid, with a relatively low density. Diamond is the form of highest density; its high refractive index and its hardness are what give it its great value. Diamond is an electrical insulator — but graphite conducts. Charcoal has the ability to adsorb gases.
Chemical properties
- Carbon is an element of low reactivity. At very high temperatures it combines with oxygen, but it shows no reaction with acids, bases or chlorine. The amorphous forms, such as charcoal, do react chemically.
- Charcoal, strongly heated and burnt, reacts with oxygen to form carbon dioxide gas.
- At high temperature, carbon reacts with calcium oxide to form calcium carbide.
Uses
| Form of carbon | Uses |
|---|---|
| Amorphous carbon | Producing black paints; as a filler in rubber |
| Coal | As a fuel |
| Graphite | Making pencils; making electrodes for electric cells; as a lubricant |
| Diamond | Jewellery; cutting gems and glass; as bearings at points of wear in machinery and balances |
| Charcoal | Absorbing gases; purifying water |
| Nano-scale carbon fibres and carbon nanotubes | Producing goods strengthened with nano materials; the fibres are extremely light and very strong |
Table 3.5 — some uses of carbon.