Assuming the validity of Bohr's atomic model for hydrogen like ions the radius of Li^++ ion in its ground state is given by 1/X a_0, where X = ____.…

Assuming the validity of Bohr's atomic model for hydrogen like ions the radius of $\displaystyle \mathrm{Li}^{++}$ ion in its ground state is given by $\displaystyle \frac{1}{\mathrm{X}} \mathrm{a}_0$, where $\displaystyle \mathrm{X}=$ $\displaystyle \_\_\_\_$. (Where $\displaystyle \mathrm{a}_0$ is the first Bohr's radius.)