Physics - Modern Physics Question with Solution | TestHub

The ionization energy for a hydrogen-like species (an atom or ion with only one electron) with atomic number $Z$ is given by $13.6Z^2$ eV.

For 10 times ionized sodium (Na¹⁰⁺), the atomic number $Z=11$.

Thus, the ionization energy is $13.6\times (11{)}^2=13.6\times 121=1645.6$ eV.