Why does carbon form compounds mainly by covalent bonding?

Hint: Covalent bond is the bond formed by the sharing of electrons between the bonding atoms. Carbon combines with hydrogen atoms and also some hetero atoms such as nitrogen, oxygen to from organic compounds which are bonded by covalent bonding.

Complete step by step solution:
The reason for carbon forming covalent bonds mainly is the electronegativity difference between the bonding atoms. As carbon mainly forms hydrocarbons and other organic compounds, the atoms bonded in the chains of these compounds are hydrogen and oxygen. The electronegativity value of hydrogen is 2.20 and the electronegativity value for carbon is 2.55. The difference is so small that it is in fractions and are comparable, when the electronegativity of any two atoms participating in bonding are comparable they share the unpaired electrons to form covalent bonding.
This can be understood by considering taking an example of ionic compounds. Let us consider an example of ionic compounds such as HCl, in hydrogen chloride, hydrogen atom and chlorine atom are bonded by electrovalent ionic bonds. The electronegativity of H is 2.55 and that of Cl is 3.16 the difference is much so the more negative chlorine attracts the electrons from hydrogen towards itself. This attraction leads to development of opposite positive and negative charges on hydrogen and chlorine respectively. The opposite charged species then attract to bind close to each other forming ionic compounds.
Therefore, carbon forms compounds mostly by covalent compounds.

Note: Bonding in chemical compounds is of three main types- ionic or electrovalent bonding, covalent bonding and dative or coordinate covalent bonding. In these three carbon forms its compounds mainly by covalent bonding by sharing an electron pair between carbon and its bonding atoms.