What is the electron configuration for a sodium ion?

The of a neutral sodium atom is ##1s^2 2s^2 2p^6 3s^1##.

In this configuration we note that there is only one electron in the 3rd energy level. Atoms prefer to gain the stability of octet, by having eight electrons in the outer shell, the electrons of the s and p orbitals. These are referred to as the valence orbitals and the .

In the case of sodium the one lone electron in the 3s valence shell would easily be released in order for sodium to have a filled valence shell at ##2s^2 2p^6##.

Therefore , the electron configuration of the sodium ion is ##1s^2 2s^2 2p^6##.

Because sodium gives up the electron from the 3s orbital it now has only 10 electrons but still has 11 protons, giving it a +1 charge and it becomes a ##Na^(+)## cation.