Magnesium reacts with an element (X) to form an ionic compound. If the ground state electronic configuration of (X) is $1{\mathrm{s}}^{2}2{\mathrm{s}}^{2}2{\mathrm{p}}^3$, the simplest formula for this compound is: 

1. ${\mathrm{Mg}}_2{\mathrm{X}}_3$

2. ${\mathrm{MgX}}_2$

3. ${\mathrm{Mg}}_2\mathrm{X}$

4. ${\mathrm{Mg}}_3{\mathrm{X}}_2$

The incorrect match among the following is:

1. B < C < N < O (increasing first ionisation enthalpy)

2. I < Br < F < Cl (increasing electron gain enthalpy)

3. Li < Na < K < Rb (increasing metallic radius)

4. Al³⁺ < Mg²⁺ < Na⁺ <F^- (increasing ionic size)