English: Carbon is the base of all life and the element with the most complex chemistry, which is called organic chemistry. Coal, which consists mostly of carbon, is known and used since prehistoric time. The massive combustion of coal and oil, which is carbon based, causes enormous harm to the life on our planet. This is because, amongst others, a lot of carbon dioxide, CO
2, is emitted.
Graphite, which is very soft, is the most common carbon allotrope. Another one is diamond, famous for its value and hardness. Fullerenes are further allotropes, which were discovered in 1985. They could have many different applications in the future.
Compounds of carbon and another, more electropositive element are called carbides. Such with elements of the first three groups are salt-like and react with water. Of the others, some are extremely hard and durable, like silicon carbide and tungsten carbide.
The natural, radioactive isotope
14C, which has a half-life of 5730 years, is absorbed in small amounts by every organism. The abundance of this in old organic material allows a good specification of its age in a span between 300 and 50,000 years. This makes it an important tool for archaeology.