Episode #125 of the Stack Overflow podcast is here. We talk Tilde Club and mechanical keyboards. Listen now
2 of 4 converted latex font

Hybridization of Tetraamminecopper(II) sulfate

$\ce Cu2+ $ has 9 electrons and d orbital in almost completely filled (except 1 electron vacant) and $NH3$ donates electron eventually forming Sp3 hybrid orbitals
But it has square planar geometry hence completely contradicting the above reasoning.Please explain what is the hybridization.