If the energy of a hydrogen atom in nth orbit is $E_n$, then energy in the nth orbit of a singley ionized helium atom will be

$4 E_n$ $E_n / 4$ $2 E_n$ $E_n / 2$

$4 E_n$

$E_n \propto Z^2 \quad \Rightarrow \quad \frac{\left(E_n\right)_{H e}}{\left(E_n\right)_H}=\frac{Z_{H e}^2}{Z_H^2}=4 \quad \Rightarrow$ $\left(E_n\right)_{H e}=4 \times\left(E_n\right)_H$