Is \[{d^3}s\] hybridisation possible ?

Hint: The term ‘hybridization’ referred to as the process of mixing of atomic orbitals which have minute differences in their energies and these energies are redistributed as to form new atomic orbitals of equivalent energies and have similar shape The concept of hybridization came into existence because valence bond theory failed to predict the molecular structure of some molecule.

Complete answer: The chemical name of the compound with structure $Cr{O_2}C{l_2}$ is chromyl chloride. It is a coordinate compound with tetrahedral geometry. It is an inorganic compound.The chromium atom $Cr{O_2}C{l_2}$ in undergoes \[{d^3}s\] hybridisation. The oxidation state of chromium in chromyl chloride is +6. The electronic configuration of chromium is given as $[Ar3{d^5}4{s^1}]$ In \[{d^3}s\] hybridization of chromium, the atomic orbitals involved are $4s,3{d_{xy}},3{d_{yz}}$ and $3{d_{_{zx}}}$ .
 Let us take another example of a compound named Potassium manganate , ${K_2}Mn{O_4}$ . In this Manganese has an electronic configuration of \[4{s^2}3{d^5}\] . In its first oxidation state 1 electron on \[4s\] moves to \[\;4p\] . Therefore hybridisation of \[s{p^3}\] is definitely not possible as only 1 electron is present in \[\;4p\] . Therefore the only way left is to intermix the 4s orbital with 3 3d orbitals viz dxy dyz and dzx. Therefore a \[{d^3}s\] hybrid orbital is formed with 4 electrons. 4 oxygen atoms will have a total of 8 unpaired electrons (each having 2). One of the unpaired electrons will combine with the \[{d^3}s\] orbital thus 4 unpaired electrons of 4 oxygen will combine with all the 4 electrons of the \[{d^3}s\] . The remaining unpaired oxygen electrons will undergo sideways overlap to form pie bonds. Therefore the hybridisation of both MnO4 2- and MnO4- is \[{d^3}s\] .

Note:
You might get confused about which hybridisation is taking place in chromyl chloride ..As the complex has tetrahedral geometry, you might think that the central chromium atom undergoes $s{p^3}$ hybridisation. That is not true. The central chromium atom undergoes \[{d^3}s\] hybridization.