Explain why carbon forms compounds mainly by covalent bond. Explain in brief two main reasons for carbon forming a large number of compounds. Why does carbon form strong bonds with most other elements?

Carbon forms compounds mainly by covalent bonding because of its electronic configuration. Carbon has an atomic number of 6, with 4 electrons in its outermost shell. To attain a noble gas configuration, it must either gain or lose 4 electrons.

1. It cannot gain four electrons to form a $C^{4-}$ anion because it would be difficult for the nucleus with six protons to hold onto ten electrons.
2. It cannot lose four electrons to form a $C^{4+}$ cation because it would require a large amount of energy to remove four electrons, leaving a nucleus with six protons holding only two electrons.

Therefore, carbon overcomes this by sharing its valence electrons with other atoms, forming covalent bonds.

Two main reasons for the large number of carbon compounds:

1. Catenation: Carbon has the unique ability to form bonds with other atoms of carbon, giving rise to large molecules in the form of long chains, branched chains, or rings.
2. Tetravalency: Since carbon has a valency of four, it is capable of bonding with four other atoms of carbon or atoms of other mono-valent elements like hydrogen, oxygen, nitrogen, and chlorine.

Carbon forms strong bonds with most other elements because of its small size. This small size enables the nucleus to hold onto the shared pairs of electrons strongly, making the resulting compounds exceptionally stable.