NEET2006Chemistryd and f Block ElementsActual
In which of the following pairs are both the ions coloured in aqueous solution- [At. No. : ( Sc =21, Ti =22, Ni =28, Cu =29, Co =27 )]
Options
- A( Ni ²⁺, Ti ³⁺ )
- B( Sc ³⁺, Ti ³⁺ )
- C( Sc ³⁺, Co ²⁺ )
- D( Ni ²⁺, Cu ⁺ )
Correct answer
A. ( Ni ²⁺, Ti ³⁺ )
Step-by-step solution
Ti ³⁺=1 s^2, 2 s^2 2 p^6, 3 s^2 3 p^6 3 d^1 Sc ³⁺=1 s^2, 2 s^2 2 p^6, 3 s^2 3 p^6 (Unpaired electron absent in d-orbital) Cu ⁺=1 s^2, 2 s^2 2 p^6, 3 s^2 3 p^6 3 d¹⁰ Thus, Cu ⁺ has completely occupied d -orbital. Hence, in the above ions, Ni ²⁺ and Ti ³⁺ ions are coloured ions in the aqueous solution because of the presence of unpaired electrons in the d -subshell. Related Theory Whenever light falls on the transition element compounds electrons absorb energy and excite. When these electrons de-excite they release v