Question

The octet rule is most likely to fail occasionally for which of the following elements?

N

C

Na

S

Answer 1

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answer: Sulphur(S)

Elements in periods greater than period 3 on the periodic table have a dorbital available with the same energy quantum number. there are conditions where they can expand their valence shells to accommodate more than eight electrons.

Sulfur is an example of this behavior. Sulfur can follow the octet rule as in the molecule SF2 where it is surrounded by 8 electrons. sulfur atom can be sufficiently excited to push valence atoms into the d orbital to allow formation of molecules such as SF₄ and SF₆. The sulfur atom in SF₄ has 10 valence electrons and 12 valence electrons in SF₆.