The radius of hydrogen atom is 0.53A⁰. The radius of${ }_3{\mathrm{Li}}^{2+}$ is of

The radius of hydrogen atom = 0.53 $\stackrel{0}{\mathrm{A}}$ ${ }_3{\mathrm{Li}}^{+2}$ ion also has only one electron but it has 3 protons in nucleus, hence its electron feels three times more attraction from nucleus in comparison of hydrogen atom. Thus, the radius of${ }_3{\mathrm{Li}}^{+2}\text{ will be }=\frac{0.53}{3}=0.17\text{Å}$