Two atoms have the electron configurations `1s^2 2s^2 2p^6 and 1s^2 2s^2 2p^6 3s^1.` The first ionization energy of one is 2080 kJ/mol and that of the other is 496 kJ/mol. Match each ionization energy with one of the given electron configurations. Justify your choice.

Explanation

The element with the configuration `1s^2 2s^2 2p^6` will have the first ionization energy value of 2080 kJ/mol. It is evident that the outer configuration is `2p^6` and hence this is an inert gas. The extra stability of a completely filled shell results in a very high value of `IE_1.`
The element with the electronic configuration `1s2 2s^2 2p^6 3s^1` will have the first ionization energy value of 496 kJ/mol. It is clear and evident that the valence third shell has only one electron and its loss will result in the element gaining noble gas configuration. So, the value of `IE_1` for this element must be a small value.