To determine which of the given molecules has a Lewis structure that does not follow the octet rule, we need to assess each option:
- a) CCl2F2: Carbon (C) has four valence electrons, and it can form four bonds to achieve an octet. In CCl2F2, carbon is surrounded by two chlorine atoms and two fluorine atoms, giving it a complete octet.
- b) BeF2: Beryllium (Be) has two valence electrons and tends to form only two bonds. In BeF2, beryllium is bonded to two fluorine atoms, so it does not complete an octet (Be has only 4 electrons around it).
- c) NF3: Nitrogen (N) has five valence electrons. In NF3, nitrogen forms three bonds with fluorine atoms and has one lone pair, giving it a complete octet.
- d) SiCl4: Silicon (Si) has four valence electrons. In SiCl4, silicon forms four bonds with chlorine atoms, achieving an octet.
Based on the analysis, the molecule with a Lewis structure that is not consistent with the octet rule is BeF2, as beryllium does not reach an octet in this structure.