Question

Atomic numbers of oxygen atom is $8$ and that of sodium atom is $11$. Predict which one would form an anion which one would a cation.

Answer 1

Oxygen

$1s^{2}2s^{2}2p^4$

To complete the octet it needs two electrons. So, it will gain two electrons to form an anion for completing its octet. Anion:- $O^{2-}$.

$Na$ (Sodium)

$1s^{2}2s^{2}2p^{6}3s^1$

It has $11$ electrons, so to become more stable it donates one electron and form a cation $N{a}^{+}$.