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

First we have to know what is the definition of the hypervalent, then how to check whether the molecule is hypervalent or not and which molecule shows hypervalency and structure of the molecule.

Complete step-by-step answer:
First starting with the definition of the hypervalent molecules.
Hypervalent molecules: any molecule which shows the property of bonding more than four bonds, i.e, the total number of the shared electrons are more than eight are called hypervalent molecules.
Mostly the molecules which p-block shows these properties.
So, now how to find the molecule is hypervalent or not:
Take the central atom of the molecule, count the number of electrons shared and if the number of electrons are more than eight than the molecule is hypervalent.
Now, moving towards the options,
In first, the chlorine is the central atom, having $7$ valence electron and it is bonded with four oxygen atoms and a negative charge on it. Hence, the shared atoms are $14$. Hence, it’s a hypervalent molecule.
Similarly, here boron is a central atom, having $3$ valence electron and it is bonded with three fluorine atoms. Hence, the shared atoms are $6$. Hence, it’s not a hypervalent molecule.
Similarly, here sulphur is a central atom, having $6$ valence electron and it’s bonded with four oxygen atoms and two negative charges on it. Hence, the shared atoms are $12$ . Hence, it’s a hypervalent molecule.
Similarly, here carbon is a central atom, having $4$ valence electron and it is bonded with three oxygen atoms and two negative charges on it. Hence, the shared atoms are $8$. Hence, it’s not a hypervalent molecule.
Hence, the $1.Cl{O_4}^ -$ and $3.S{O_4}^{2 - }$ are hypervalent molecules.

Hence, the correct option is (b) $1,3$.

Note: Hypervalent molecules are the molecules having more than four covalent bonds present in the molecules and also there are molecules which are having less than four covalent bonds known as hypervalent molecules.