The species which does not exist is

Amongst the following the total number of species which does/do not exist is : SF_6,BF_6^(3-), SF_4, OF_4, AIF_6^(3-),PH_5, PCl_5, NCl_5, SCl_6

Which does not exists

Which is does not exist

The fluoride which does not exist is

The fluoride which does not exist is

Which one does not exist

Which species does not exist ?

Which species does not exist ?