Here's my understanding:
- An ion with a negative charge has gained electrons. Hence the negative charge.
- With a greater negative charge, there should be more attraction towards the positive charge.
- As a result the electrons should be pulled towards the positively charged electrons.
- Ionic radius should decrease.
- Further an ion gains an electron to achieve a full shell. So the number of shells remains constant.
I understand that this is wrong. However, what is wrong with this intuition? Why does the ionic radius increase when the charge becomes more negative and decrease when the charge becomes more positive?