Question

What are the possible oxidation numbers of carbon?

Answer 1

Carbon has a unique property called catenation due to which it forms covalent bonds with other carbon atoms. Due to this property, it can also form covalent bonds with the atoms of other elements like hydrogen, oxygen, halogens, phosphorus, nitrogen, and sulphur, etc. Catenation is the property by virtue of which atoms of the same elements can form chemical linkage in chains or rings.

Complete Step By Step Answer:
Carbon has atomic number 6 and it's ground state electronic configuration is $1{s^2}2{s^2}2{p_x}^12{p_y}^12{p_z}^0$ . Since a carbon atom has four electrons in its outermost shell, the valency of the carbon atom is four. Therefore, to attain noble gas configuration, a carbon atom can either gain four electrons to form ${C^{4 - }}$ ion or lose four electrons to form ${C^{4 + }}$ ions.
But these processes i.e. electron gain enthalpy and ionization enthalpy require a large amount of energy. Thus, the carbon atom has very little tendency to form ionic compounds. Therefore, the carbon atom can achieve noble gas configuration by sharing its valence shell electrons with other carbon atoms or atoms of the other elements. Hence, carbon can form four covalent bonds in its compounds. This is another unique property of a carbon atom called tetravalency. Tetravalency is the property by virtue of which a carbon atom can form four covalent bonds in its compound by sharing its valence shell electrons with the atoms of the other elements.

Note:
Metals are electropositive which means they have the tendency to lose electrons to form positively charged ions whereas non-metals are electronegative which means that they have the tendency to lose electrons to form negatively charged ions. Group 18 elements are called noble gases because of their filled octet.