Which of the following species has the highest ionisation potential?

Options

A. Li
B. `Mg^(+)`
C. `A1^(+)`
D. Ne

Answer

A

Explanation

`Li = 1s^(2) 2s^(1)`
`Mg^(+) =1s^(2) 2s^(2) 2p^(6) 3s^(2)`
`Al^(+) = 1s^(2) 2s^(2) 2p^(6) 3s^(2)`
`Ne=1s^(2) 2s^(2) 2p^(6)`
In the periodic table, helium has the highest ionization potential.
Moreover lithium contains the same configuration as helium and has one extra electron in 2s orbital.
therefore Li has the highest ionisation potential.