Explain the octet rule for formation of —

(a) Sodium chloride from a sodium atom and a chlorine atom.

(b) Nitrogen molecule from two nitrogen atoms.

(a) As Na atom has atomic number 11 and electronic configuration [2, 8, 1]. Therefore, it tends to lose 1 electron from its valence shell forming Na¹⁺ (cation) to attain a stable octet configuration of the nearest noble gas Neon [2, 8].

Cl, on the other hand has atomic number 17 and electronic configuration [2, 8, 7]. Therefore, it tries to gain one electron in its valence shell forming Cl^1- (anion) to attain a stable octet configuration of the nearest noble gas Argon [2, 8, 8].

The oppositely charged cation and anion attract each other with a force - [electrostatic force of attraction] resulting in formation of an ionic or electrovalent compound [NaCl] as shown below.

(b) Nitrogen atom (¹⁴₇N) has atomic number 7 and electronic configuration [2, 5]. To attain stable octet structure of the nearest noble gas Neon [2, 8], Nitrogen needs three electrons in the valence shell. Nitrogen atom shares electron pairs with other nitrogen atom resulting in the formation of a molecular or covalent bond as shown below: