The increasing order of non-metallic character of the elements N, P, O, and S is: 

1. P < S < N < O

2. O < S < N < P 

3. O < N < S < P 

4. N < S < O < P

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 formula of the stable binary compounds that would be formed by 
an element having atomic number 71 and fluorine: