The ionisation energy of `He^(o+) is `19.6 xx 10^(-19) J "atom "^(-1)` .Calculate the energy of the first stationary state of `li^(2+)`

Explanation

`E_(1)` for `Li^(2+) = E_(1)` for `H xx Z^(2) = E_(1)` for `H xx 9`
`E_(1)` for `He^(o+) = E_(1)` for `H xx Z^(2) = E_(1)` for `H xx 4`
` :. E_(1)` for` Li^(2+) = E_(1)` for `He^(o+) xx (9)/(4)`
`19.6 xx 10^(-19) xx (9)/(4)`
`= 44.1 xx 10^(-19) J "atom"^(-1)`