There was a question which was asking about the order of ionization energies of K,Li,Ca,S. The electronic configuration of all the elements were as follows
- Li:${1s^2 2s^1}$
- K :${1s^2 2s^2 2p^6 3s^2 3p^6 4s^1}$
- Ca :${1s^2 2s^2 2p^6 3s^2 3p^6 4s^2}$
- S :${1s^2 2s^2 2p^6 3s^2 3p^4}$
From the electronic configurations:
Potassium should have lowest ionization energy as it is very easy to remove electron from 4th shell.
Then it should be followed by Calcium as its nuclear charge increases from going across the period
Then it should be followed by sulphur as it is more easier to remove the electron from 3rd shell than from 2nd shell.
Then it should be followed by Lithium as it has lowest principle quantum number(n) so it is more difficult to remove an electron from 2nd shell than from 3rd and 4th shell.
So according to my calculation the order should be K < Ca < S < Li. But the correct answer in my textbook is K < Li < Ca < S. If I am wrong anywhere then what factor would help in determining the Ionization energies of the following elements, and what would be the exact order of I.E for these elements.