Question

What is the hybridisation of P in Po4 3- ?

Answer 1

Hybridization of Phosphorus = sp3 

Hybridization of oxygen is sp3 and sp2 

The double bonded oxygen is sp2 

And negative charged oxygen is sp3 hybridized  

Phosphorus can expand its valency because of vacant d orbitals 

Oxygen forms a double bond with the phosphorus in which oxygen-phosphorus bond is like a coordinate bond in which the oxygen donates its electrons to the vacant d-orbitals of phosphorus  

So the pi bond is said to be pπ - dπ bond.