- Asked 2/16
- 2071 Bhadra · 2.5 marks
- 2067 Mangsir · 2 marks
TiO₂ white but TiCl₃ violet
Short answer
TiO₂ contains Ti⁴⁺ (3d⁰), so no d–d transition occurs; it reflects all visible light and appears white. TiCl₃ contains Ti³⁺ (3d¹); in aqueous [Ti(H₂O)₆]³⁺ the d electron absorbs green-yellow light, transmitting the complementary violet colour.
Give reason: TiO₂ is white but TiCl₃ is violet.
- TiO₂ is white: titanium is in the +4 state, Ti⁴⁺ is 3d⁰. There are no d electrons, so no d–d transition is possible and visible light is not absorbed (all wavelengths reflected), giving white.
- TiCl₃ is violet: titanium is in the +3 state, Ti³⁺ is 3d¹. In solution as [Ti(H₂O)₆]³⁺ the single d electron lies in the t₂g level. It absorbs green-yellow light (around 500 nm) to jump to the e_g level, and the complementary violet (purple) colour is seen.
✓ Answer checked by Claude Opus 5.5 (high effort)