The one electron species having ionization energy of 54.4 eV is :

Options

A. `H `
B. `He ^(+)`
C. `B^(4+)`
D. `Li ^(2+)`

Answer

B

Explanation

Out of other alternates, `He ^(+)` has ionisation energy of `54.4 eV` because in `He ^(+)` effective nuclear charge is fairly high and ionic size is small.