Question

Ca²⁺ has completely filled outer shell. Justify your answer.

Answer 1

The atomic number of Calcium is 20. It has K = 2, L = 8, M = 8, N = 2.
If we remove the last 2 electrons, that is from the N shell, Ca2+ and we will be having 8 in the outermost shell (M shell). So we have completely filled the outer shell. (The maximum 8 electrons in a shell is a completely filled shell).