The electronic configurations of two elements $\mathrm{X}$ and $\mathrm{Y}$ are given below:

$\mathrm{X}=1{\mathrm{s}}^{2}2{\mathrm{s}}^{2}2{\mathrm{p}}^{6}3{\mathrm{s}}^{2}3{\mathrm{p}}^{6}4{\mathrm{s}}^2 ; \mathrm{Y}=1{\mathrm{s}}^{2}2{\mathrm{s}}^{2}2{\mathrm{p}}^{6}3{\mathrm{s}}^{2}3{\mathrm{p}}^5$

The formula of the ionic compound formed between these elements is: