2) Stability of the fully-filled orbitals d block elements donate electrons from 4s orbitals to form cations. Example: Zn : 1s 2s 2p 3s 3p 4s 3d 10 6 2 6 2 2 2 6 2 2 Zn 2+ : 1s 2s 2p 3s 3p 3d 10 6 2