CBSE Class 10 Science 2022 · Paper 31(B)/5 · Question 1(b)

Carbon has atomic number $6$ and electronic configuration $2,4$, so it has four electrons in its outermost shell. To form an ionic bond it would have to become an ion by transferring four electrons, and neither way is favourable: 1. It could gain four electrons to form the anion ${\text{C}}^{4-}$. But it would be difficult for a nucleus with only six protons to hold on to ten electrons, that is, four extra electrons. 2. It could lose four electrons to form the cation ${\text{C}}^{4+}$. But removing four electrons needs a very large amount of energy, and it would leave six protons holding on to just two electrons. So the carbon atom does not form ionic bonds. Instead it shares its four valence electrons with other atoms and forms covalent bonds; in methane (${\text{CH}}_4$), for example, it shares one pair of electrons with each of four hydrogen atoms.