|Atomic mass||12.01115 amu|
Carbon is a solid non-metal element. It's been known since prehistoric times.
Carbon exists in three allotropic forms:
- buckminsterfullerene, or also known as "bucky ball"
The three allotropic forms differ from one another in the arrangement of the carbon atoms in their crystals.
Diamond is one of the hardest substances known and a poor conductor of electricity. Diamond is a gemstone. It is also used in old phonograph needles. Heated to 1800°C, diamond transforms to graphite.
At room temperatures and pressures, graphite is the most stable allotrope of carbon. It is soft, black, slippery and much less dense than diamond. The carbon atoms in graphite are arranged in layers, thus, giving graphite the ability to conduct electricity within the layer. Layers easily slide over each other. As a result, graphite is used as a lubricant, as an additive for motor oil and in pencil "lead".
- Main article: Buckminsterfullerene
This soccer-ball shaped molecule has potential applications in electronics, catalysis, polymers, and medicines.
Carbon makes up about 0.08% of the combined lithosphere, hydrosphere, and atmosphere. It occurs in the crust of the earth mainly in coal and petroleum and in the form of calcium carbonate, or magnesium carbonate rocks. Marble, limestone, chalk, coral are found in enormous deposits throughout the world. Many of these compounds are remnants of fossilized marine organisms.
Carbonates are used in common antacids because they react with acid such as stomach acid (hydrochloric acid, HCl). At the same time, by similar reactions with sulfuric and nitric acids from acid rain, limestones which protect lakebeds are destroyed.
Carbon dioxide, of course, is essential to all life as the ultimate source of carbon in plants and animals through its role in photosynthesis. Carbon dioxide in aqueous solution is also the cause of acidity in natural waters. In the atmosphere, carbon dioxide can be built up from deforestation and excessive use of fossil fuels. This may severely affect the climate through what is known as the "greenhouse effect".
Other uses of carbon include:
- graphite composites
- graphite electrodes
- steel, which is an alloy of iron and carbon
- graphite control rods in nuclear reactors
- an abrasive material known as carborundum (silicon carbide)
- petroleum products
The list becomes endless because the variety of carbon-containing compounds are so varied in everyday products.