For the following molecules/ions,identify whether the octet rule is obeyed or not obeyed. Provide the reason.
$(1)$ $PCl_5$ $(2)$ $SF_6$ $(3)$ $PF_5$ $(4)$ $NH_4^+$ $(5)$ $BeCl_2$ $(6)$ $NCl_3$

(N/A) The octet rule states that atoms tend to gain,lose,or share electrons to achieve a stable configuration of $8$ electrons in their valence shell.
$(1)$ $PCl_5$: Phosphorus has $10$ electrons in its valence shell (expanded octet). Rule not obeyed.
$(2)$ $SF_6$: Sulfur has $12$ electrons in its valence shell (expanded octet). Rule not obeyed.
$(3)$ $PF_5$: Phosphorus has $10$ electrons in its valence shell (expanded octet). Rule not obeyed.
$(4)$ $NH_4^+$: Nitrogen has $8$ electrons in its valence shell. Rule obeyed.
$(5)$ $BeCl_2$: Beryllium has $4$ electrons in its valence shell (incomplete octet). Rule not obeyed.
$(6)$ $NCl_3$: Nitrogen has $8$ electrons in its valence shell. Rule obeyed.