Which electrons get removed to form Ar+ and Ar2+?

1 Answer
May 26, 2016

Argon (Ar) has the atomic number 18 (it's right by chlorine and neon). By default, its electron (script) configuration is written as 1s22s22p63s23p6.

Any electron removed during an ionization is from the orbital that is currently highest in energy.

You can see in Appendix B.9 here that the energy of the 3p orbital is higher by 13.42 eV (1294.83 kJ/mol).

So, the 3p electrons will get removed:

Ar+: 1s22s22p63s23p5

Ar2+: 1s22s22p63s23p4

As a general observation, the energies for orbitals of the same principal quantum number n are usually:

End>Enp>Ens