The ionisation energy of `H` is `13.6 eV`. Calculate the ionization energy of `Li^(2+)` ions.

Explanation

`Li overset(-e^(-))Li^(+) overset(e^(-)) Li^(2+) overset(e^(-))to Li^(3+)`
Total energy required `=1.96 xx 106(4)=19600"kJ mol"^(-1)`
`I.E_(1)=520kJ mol^(-1), I.E_(3)=(1312 xx Z^(2))/(n^(2))=(1312 xx 9)/(1) =11808`
`I.E_(1)+I.E_(3)=12328kJ mol^(-1)`
`I.E_(2)=19600-12328=7272"kJ mol"^(-1)`