# What is the hybridization of copper in blue vitriol?

My book says that the structure of blue vitriol is the following:

From the structure, I figured that since there are 4 water molecules coordinated to the cuprate ion, the hybridization should be $$sp^3$$. But when I googled, I saw that people were saying its hybridization is $$sp^3d^2$$. Why would that be true?

• Can the downvoter explain what mistake I made? Sep 17 at 13:14

In the diagram above you can see that copper has a charge of +2 i.e. Cu$$^{2+}$$ which leads to a 3d$$^9$$ configuration. Since H$$_2$$O will here act as a weak field ligand, no pairing of electrons will be done in d-orbitals which will lead to sp$$^3$$d$$^2$$ hybridization.