The potential energy of the electron present in the ground state of Li⁺² ion is represented by :

The potential energy of an electron in the ground state of hydrogen-like atoms  is given by  
$-\frac{Z{e}^2}{4\mathrm{\pi }\in \circ \mathrm{r}}$

​The -ve sign of potential energy reflects the stability of the electron in the ground state due to the coulombic force of attraction between the nucleus and electron.

for Li ²⁺  Z=3, where Z=atomic number of an atom

Thus the potential energy of the electron present in the ground state of Li⁺² ion is  $-\frac{3{\mathrm{e}}^2}{4\mathrm{\pi }{\in }_{\circ }\mathrm{r}}$