Which one of the following is an outer orbital complex and exhibits paramagnetic behaviour?
- [Ni(NH3)6]2+
- [Zn(NH3)6]2+
- [Cr(NH3)6]3+
- [Co(NH3)6]3+
Answer
(1) [Ni(NH3)6]2+
Solution
Ni2+: 3d8; the two inner 3d orbitals are not free even after pairing sp3d2 (outer orbital) with 2 unpaired electrons paramagnetic.
Zn2+: 3d10 outer orbital but no unpaired electron diamagnetic.
Cr3+: 3d3 two 3d orbitals free d2sp3 (inner orbital), paramagnetic.
Co3+: 3d6 with NH3 d2sp3 (inner orbital), diamagnetic (as per NCERT).
only [Ni(NH3)6]2+ is outer orbital and paramagnetic.
Answer: (1)