The aqueous solution containing which one of the following ions will be colourless? (Atomic number : Sc = 21, Fe = 26, Ti = 22, Mn = 25)
- Sc3+
- Fe2+
- Ti3+
- Mn2+
Answer
(1) Sc3+
Solution
Colour of transition metal ions arises from d–d transitions, which need partly filled d orbitals.
Sc3+: 3d0, Fe2+: 3d6, Ti3+: 3d1, Mn2+: 3d5
Sc3+ has no d electron, no d–d transition is possible
As per NCERT, Sc3+ (aq) is colourless.
Answer: (1)