State the reason why carbon forms a covalent compound and not`C^(4+) and C^(-4)`. Also give reasons why covalent compounds are bad conductors of electricity and have law melting and low boiling points.

Explanation

Atomic number of carbon is 6. It has four electrons in its outermost shell and it needs four more electrons to attain noble gas electronic configuration. It does not form `C^(4+)` cation, as the removal of four valence electrons will require huge amount of energy.
Carbon is unable to form `C^(4+)` anion as its nucleus with six protons will not be able to hold ten electrons due to its small size.
Therefore carbon achieves noble gas electronic configuration by sharing its four electrons either with same or different atoms. Therefore it forms covalent compounds.
i] Covalent compounds do not have free ions, due to this they are bad conductors of electricity in solid, molten or aqueous state.
ii] Covalent compounds have covalent bond. In these compounds the inter molecular forces of attraction is weak. Thus low amount of energy is required to break there forces of attraction. Hence, their melting and boiling points are quite low.