Which of the following molecules has a central atom with complete octet?

Which of the following molecules has a central atom with complete octet?
  1. Methane
  2. Sulphur hexafluoride
  3. Aluminium chloride
  4. Boron trifluoride

Solution

$\mathrm{SF}_{6}$ - Expanded octet of $\mathrm{S}$ $\mathrm{BF}_{3}, \mathrm{AlCl}_{3} \rightarrow$ Incomplete octet of $\mathrm{B}$ and $\mathrm{Al}$ respectively. $\mathrm{CH}_{4}-$ Complete octet of $\mathrm{C}$.

Asked in: MHT CET 2020 (19 Oct Shift 2)

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