# The ionization energy of H atom is $13.6eV$.What will be ionization energy of $He^+$ and $Li^{2+}$ ions?

$\begin{array}{1 1}(a)\;60.3eV,124eV&(b)\;54.4eV,122.4eV\\(c)\;72.4eV,120eV&(d)\;72.4eV,121.34eV\end{array}$

$E_1$ for $He^+=E_1$ for $H\times z^2$
$\Rightarrow13.6\times 4=54.4eV$
$E_1$ for $Li^{2+}=E_1$ for $H\times z^2$
$\Rightarrow13.6\times 9=122.4eV$
Hence (b) is the correct answer.