Question

What is the hybridisation of $SO_4^{2 - }$ ion?

Answer 1

To know the characteristic geometrical shapes of polyatomic molecules the concept of hybridisation was introduced. The atomic orbitals combine to form a new set of equivalent orbitals known as hybrid orbitals. Hybridisation is a process of intermixing of the orbitals of slightly different energies so that it redistributes the energies resulting in the formation of new orbitals of equivalent energies and shape.
Example- one $2s$ and three $2p$ orbitals of carbon hybridise to form four new $s{p^3}$ hybrid orbitals.

Complete answer:
Sulphate($SO_4^{2 - }$) is one of the most widely naturally available chemical compounds.
Sulphate is basically a chemical compound that is composed of sulphur and oxygen atoms. Sulphate forms salts with a variety of elements .
The number of sigma bond and lone pair electrons provides details regarding ion hybridisation.
$sp$ hybridisation- Number of sigma bond and lone pair of electrons is 2.
$s{p^2}$ hybridisation- Number of sigma bonds and lone pair of electrons is 3.
$s{p^3}$ hybridisation- Number of sigma bonds and lone pair of electrons is 4.
According to VSEPR theory the $SO_4^{2 - }$ ion has tetrahedral molecular geometry. The $SO_4^{2 - }$ ion has four oxygen atoms arranged tetrahedrally around the sulphur atom. So, there are a total of four $S - O$ sigma bonds and all four bonds are of equal lengths. Hence $SO_4^{2 - }$ ion has $s{p^3}$ hybridisation. The extra two electrons of sulphur form two double bonds to oxygen then they move over to their oxygen forming a net negative charge on each of the four oxygen atoms.

Note:
In each $s{p^3}$ hybrid orbital there will be $25\%$ s-character and $75\%$ p-character. The angle between the $s{p^3}$ hybrid orbital is ${109.5^0}$. The other examples for $s{p^3}$ hybridisation is $N{H_3}$, ${H_2}O$,$C{H_4}$,${C_2}{H_6}$ molecules etc. there are hybridisation involving d orbitals. They are $ds{p^2}$,$s{p^3}d$,$s{p^3}{d^2}$ and ${d^2}s{p^3}$ hybridisation. These are the hybridisations for higher molecules.