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.

The nucleus of element with 2 electrons in 'K' shell & 1 electron in 'M' shell.

1. is ³⁹₁₉X
2. has 12 neutrons
3. has 19 protons
4. has equal no. protons & neutrons

Assertion: Elements ¹₁H, ²₁H, ³₁H have different number of neutrons.

Reason: Isotopes have the same atomic number.

1. Both A and R are true and R is the correct explanation of A.
2. Both A and R are true and R is not the correct explanation of A.
3. A is true and R is false.
4. A is false and R is true.

The element 'X' has same number of protons, neutrons & electrons, with same number of electrons in 'K' shell & 'N' shell. The element -

1. Is a non-metal with valency -2.
2. Attains stable octet structure of the nearest inert gas 'Ar', by gain of two electrons in its valence shell.
3. Is a metal with valency +2.
4. X₂₊ has electronic configuration 2, 8.