Physics - Modern Physics Question with Solution | TestHub

Energy required to remove ${\mathrm{e}}^{-}$from singly ionized helium atom $=\frac{(13.6)Z^2}{1^2}=54.4\mathrm{eV}$$(\because \mathrm{Z}=2)$ Energy required to remove ${\mathrm{e}}^{-}$from helium atom $=x\mathrm{eV}$
According to question, $54.4\mathrm{eV}=2.2\mathrm{x}\Rightarrow \mathrm{x}$$=24.73\mathrm{eV}$
Therefore, energy required to ionize helium atom $=(54.4+24.73)\mathrm{eV}=79.12\mathrm{eV}$