OCTET RULE :-
According to the octet rule, every atom tries to have 8 electrons in its outermost (or valence) shell or to achieve noble gas configuration . This may require them to lose, share, or gain electrons from other atoms.

For eg :-

Sodium(Na - 2, 8, 1)  has 1 electron in its valence shell so it loses this 1 electron to achieve octet and to become stable.
Fluorine(F - 2, 7)  has 7 electrons in its valence shell so it gains 1 electron from another atom to achieve octet and thus stability.
Nitrogen(N - 2, 5)  has 5 electrons in its valence shell so it shares 3 electrons with another Nitrogen atom such that both atoms achieve octet and hence become stable.
Neon (Ne - 2, 8)  has 8 electrons in its valence shell and since it has 8 electrons in its valence shell(complete octet) so it does not lose, gain or share electrons with any other atom and hence does not react and is considered "inert"