Question

how many d-orbitals are involved in the formation of PCl5?

Answer 1

PCl5: Phosphorus Penta chlorideCentral atom: PhosphorusAtomic number 15

ground Electronic configuration :1s²2s²2p⁶3s²3p³

Excited state:1s²2s²2p⁶3s¹3p³3d¹

hence hybridization in PCl5 is SP³d
Shape :Trigonal bipyramidal .
So one d orbitals is involved in hybridization.