Which one of the following compounds does not follow the octet rule: a) NF3 b) CF4 c) SF4 d) PH3 e) HCl?

The compound that does not follow the octet rule among the options provided is SF₄.

Here’s a brief explanation of each option:

• NF₃: Nitrogen has five valence electrons and forms three bonds with fluorine atoms, completing its octet with the shared electrons.
• CF₄: Carbon has four valence electrons and forms four bonds with four fluorine atoms, thus completing its octet.
• SF₄: Sulfur has six valence electrons and can expand its valence shell. In SF₄, it forms four bonds with fluorine and has one lone pair, resulting in a total of ten electrons around sulfur, violating the octet rule.
• PH₃: Phosphorus has five valence electrons. In PH₃, it forms three bonds with hydrogen, which does not fulfill the octet rule, but it is still an exception where the central atom is stable without completing an octet.
• HCl: Hydrogen has one valence electron, and chlorine has seven. In HCl, chlorine completes its octet by sharing one pair of electrons with hydrogen.

Therefore, SF₄ is the only compound in this list that exceeds the octet limit.