The edge length of unit cell of sodium chloride is 564 pm. If the size of ${\mathrm{Cl}}^{-}$ ion is 181 pm, the size of ${\mathrm{Na}}^{+}$ ion would be

The edge length of unit cell of sodium chloride is 564 pm. If the size of ${\mathrm{Cl}}^{-}$ ion is 181 pm, the size of ${\mathrm{Na}}^{+}$ ion would be 101 pm.

In NaCl crystal $r\left({\mathrm{Na}}^{+}\right)+r\left({\mathrm{Cl}}^{-}\right)=a/2$. Hence, $r\left({\mathrm{Na}}^{+}\right)=(564\mathrm{pm}/2)-181\mathrm{pm}=101\mathrm{pm}$

Hence, option A is correct.