The formula of the sulphate of an element X is ${\text{X}}_2{\left({\text{SO}}_{\text{4}}\right)}_3$  The formula of nitride of the element X is

The formula of sulphate of an element ‘X’ is  ${\text{X}}_2{\left({\text{SO}}_{\text{4}}\right)}_3$

Charge on ‘X’ is  $2\left(x\right)+3(-2)=0$

So that,  $x=+3$

According to Criss –cross method, the formula of nitride $({\text{N}}^{-3}\text{)}$ with the element ‘X’ is