Question

Which of the following species are hypervalent?
$1:Cl{O}_4{}^{-}$
$2:B{F}_3$
$3:S{O}_4{}^{2-}$
$4:C{O}_3{}^{2-}$

• A. 1,2,3
• B. 1,3
• C. 3,4
• D. 1,2

Answer 1

Answer: (B)

1,3

A hypervalent molecule is the one that contains one or more main group elements formally bearing more than $8$ electrons in their valence shells.

So, $Cl{O}_4^{-}$ is hypervalent as $Cl$ contains more than $8$ electrons & $S{O}_4^{2-}$ is hypervalent as $S$ contains more than $8$ electrons.