Give reason why carbon atom neither form C4+ nor C4-. (CBSE 2013)

Carbon cannot form C^{4 +} cations nor C^4- anions. The reasons are:

i. The atomic number of carbon is 6. According to electronic configuration, it has 4 electrons in its valence shell.

ii. If carbon will form C^4- anions, it has to gain four electrons. In this case, the carbon will have 6 protons and 10 electrons making it difficult for the nucleus to hold them. Thus, carbon does not form C^4- anions.

iii. If carbon will form a C^{4 +} cation, it has to lose 4 electrons. A very large amount of energy will be used to remove 4 electrons from an atom. Also then the carbon will have 6 protons with just 2 electrons again making it difficult for the nucleus.

iv. Thus, instead of losing or gaining four electrons, Carbon shares it electrons forming covalent bond.