$\text{ What is the co-ordination number of sodium in }{\mathrm{Na}}_2\mathrm{O}\text{ ? }$

${\mathrm{Na}}^{+}\text{ions are present in tetrahedral void in }$${\mathrm{Na}}_2\mathrm{O},\text{ So C.No. of }{\mathrm{Na}}^{+}=4$