In which compound forms does carbon occur?

Hint: Carbon is a p-block element which occurs in many physical forms. It is a part of an important gas in the atmosphere. It is also an important constituent in hydrocarbons and various crystalline and non-crystalline forms.

Complete step by step answer:
- Carbon is the fourth most abundant element found in nature.
- Carbon occurs in various compounds in nature. From gases to solids, it occurs as a part of carbon dioxide in the atmosphere and as a component in earth’s crust.
- Earth as a whole contains around 4360 million gigatons of carbon in various forms.
- Carbon reacts with oxygen to form carbon dioxide gas. The atmosphere contains around 0.04 percent carbon dioxide.
- Carbon is also a constituent of many rocks such as marble, limestone, dolomite, etc.
Coal is a hard rock, which is widely used as a fuel. It is mainly composed of carbon. Coal is the largest source of carbon on earth’s surface.
- Carbon also exists in its many allotropic forms such as graphite, diamond, buckminsterfullerene, etc. However, carbon mostly occurs as a tetravalent compound in nature in the form of hydrocarbons.

Additional Information: The most abundant element (by mass) found in nature is hydrogen, followed by helium and oxygen.

Note: Carbon can be found as three isotopes in nature, i.e. Carbon-12, Carbon-13, Carbon-14. Isotopes are compounds with the same number of protons but different number of neutrons. All isotopes of carbon have six protons, but have different number of neutrons -
- Carbon-12 has 6 neutrons
- Carbon-13 has 7 neutrons
- Carbon-14 has 8 neutrons