The energy of electron in n^th orbit of hydrogen atom is:

The energies of the stationary states associated with these kinds of ions (also known as hydrogen like species) are given by the expression.

${\mathrm{E}}_{\mathrm{n}}=-2.18\times {10}^{-18}\left(\frac{{\displaystyle 1}}{{\displaystyle {\mathrm{n}}^2}}\right)\mathrm{J}$