[Cr(NH3)6]3+ is paramagnetic while [Ni(CN)4]2− is diamagnetic. Explain, Why?
Hexaammine chromium (III) ion, [Cr(NH3)6]3+ ion
Oxidation state of Cr = +3
24Cr=[Ar]3d54s1
Cr3=[Ar]3d3
Cr3+ provides six empty orbitals to accommodate six electron pairs from six NH3 molecules. It involves d2sp3 hybridization and hence, octahedral
It is paramagnetic due to the presence of three unpaired electrons.
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Tetracyanonickelate (II) ion, [Ni(CN)4]2−
Ni=[Ar]3d84s2, Ni2+=[Ar]3d8
CN− being strong field ligand causes pairing of 3d electrons thus, one of the 3d−orbital becomes emplty for CN−ion.
Unpaired electron is not present so it is diamagnetic.