Q. Which one of the following is an inner orbital complex as well as diamagnetic in behaviour ? (Atomic no. : Zn = 30, Cr = 24, Co = 27, Ni = 28)
A) [Zn(NH₃)₆]²⁺
B) [Cr(NH₃)₆]³⁺
C) [Co(NH₃)₆]³⁺
D) [Ni(NH₃)₆]²⁺
Explanation
[Solution from source] Co³⁺ is 3d⁶; with NH₃ the electrons pair up in t₂g, leaving two 3d orbitals for d²sp³ (inner orbital) hybridisation with no unpaired electrons, so it is diamagnetic. [Cr(NH₃)₆]³⁺ is inner orbital but has 3 unpaired electrons; the Zn²⁺ and Ni²⁺ complexes are outer orbital. Answer (3).
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.