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🧪 Chemistry  ·  d- and f-Block Elements  ·  NEET & JEE

Crystal field theory (CFT) explains colour and magnetic properties. In an octahedral field, d orbitals split into:

Answer: t 2g (lower energy, 3 orbitals) and eg (higher energy, 2 orbitals).

  • A t<sub>2g</sub> (lower energy, 3 orbitals) and eg (higher energy, 2 orbitals)
  • B Two perfectly equal-energy sets of orbitals with no splitting at all
  • C Three separate sets of orbitals all at different energy levels
  • D An unpredictable, random pattern of orbital energies

Correct answer: A. t<sub>2g</sub> (lower energy, 3 orbitals) and eg (higher energy, 2 orbitals)

Explanation: An octahedral ligand field splits d orbitals into lower-energy t<sub>2g</sub> (dxy, dxz, dyz) and higher-energy eg (dx2-y2, dz<sup>2</sup>) sets.

Colours of Common Transition Metal Ions (Aqueous)Cu²⁺ blueFe²⁺ pale greenFe³⁺ brown-yellowMn²⁺ pale pinkNi²⁺/Cr³⁺ greenColour arises from d-d electron transitions - d⁰ ions like Sc³⁺, Ti⁴⁺ are colourless

Aqueous solutions of transition metal ions show characteristic colours caused by electrons absorbing visible light to jump between split d-orbitals; the exact colour depends on the metal, its oxidation state, and surrounding ligands.

Concept context

Transition metals (d-block) and lanthanides/actinides (f-block). Known for coloured compounds, variable oxidation states, complex formation, and catalytic properties. Frequently tested in JEE and NEET.

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