d–d transition: how a transition-metal ion gets its colourd–d संक्रमण: संक्रमण धातु आयन को रंग कैसे मिलता हैd–d transition: how a transition-metal ion gets its colour

Class 12 Chemistry · Chapter 4 · interactive diagram

Parts and what they mean

• Five d orbitals of the free ion (मुक्त आयन के पाँच d कक्षक) — In an isolated ion all five d orbitals have the same energy.
• Lower-energy d orbitals (कम ऊर्जा वाले d कक्षक) — Water ligands split the d orbitals: three lower (t₂g) and two higher (eg) in an octahedral complex. Details come in Unit 5.
• Higher-energy d orbitals (अधिक ऊर्जा वाले d कक्षक) — The gap Δ between the two sets matches the energy of visible light.
• The single 3d electron of Ti³⁺ (Ti³⁺ का एकमात्र 3d इलेक्ट्रॉन) — Ti³⁺ = 3d¹. It sits in a lower d orbital.
• d–d transition (d–d संक्रमण) — Absorbing visible light, the electron jumps from a lower to a higher d orbital.
• Energy gap Δ (ऊर्जा अंतर Δ) — The ligand decides Δ, so the same ion can have different colours with different ligands.
• Absorbed light (अवशोषित प्रकाश) — [Ti(H₂O)₆]³⁺ absorbs mainly blue-green light (498 nm).
• The solution (विलयन) — Aqueous Ti³⁺ solution.
• Colour seen = complementary colour (दिखने वाला रंग = पूरक रंग) — Red + blue light passes on, so we see violet-purple — the complementary colour of what was absorbed.

Steps

1. The d electron sits in a lower-energy d orbital (water has split the d orbitals).
2. It absorbs blue-green light and jumps to a higher d orbital.
3. The light that is not absorbed reaches our eye: we see violet.

Original diagram drawn by Simple Learning Hub, based on the NCERT textbook. Report a mistake