Q. Out of TiF₆²⁻, CoF₆³⁻, Cu₂Cl₂ and NiCl₄²⁻ (Z of Ti = 22, Co = 27, Cu = 29, Ni = 28) the colourless species are:
A) Cu₂Cl₂ and NiCl₄²⁻
B) TiF₆²⁻ and Cu₂Cl₂
C) CoF₆³⁻ and NiCl₄²⁻
D) TiF₆²⁻ and CoF₆³⁻
Explanation
[Solution from source] Ti⁴⁺ in TiF₆²⁻ is 3d⁰ and Cu⁺ in Cu₂Cl₂ is 3d¹⁰, so no d–d transition is possible and both are colourless. Co³⁺ (3d⁶) and Ni²⁺ (3d⁸) have partly filled d orbitals and are coloured. Answer (2).
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.