How do you determine the cases that violate the octet rule ?

Provide clear explanation .How do you determine the cases that violate the octet rule ?
Many compounds of group IIIA elements do by having a sextet rather than an octet. Compounds of the group VIA and VIIA elements violate it by having an ';expanded octet.';





The way to tell in either case is to count the atoms around the central atom and try to guess whether there are probably more than eight electrons. The only way to be sure is to draw out the complete Lewis structure.





You should not count H, Li, and Be as elements that violate the octet rule, because they either yield the electron configuration of He, which is a rare gas, or 0 in the case of H.

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