How to identify the atoms whic do not follow Octet rule..????
ex: SO2 , PCl3 , BCl3 , OF2 .
You have to count the valence electron of the each atomic element in their combined state, because atomic element (atomic number ˂ 20) tends to combine in such a way that each has eight electrons in their valence shell giving them electronic configuration of a noble gas.
In this case BCl3, doesn't follow octet rule.