O2→2 unpaired electrons according to MOT O2+→1 unpaired electrons according to MOT O2−→1 unpaired electrons according to MOT NO→ odd electron species NO2→ odd electron species K2[NiCl4]→Ni2+⇒3 d8 weak Ligand, C.N. =4 ⇒ Tetrahedral, Paramagnetic with 2 unpaired electrons