Chemistry of s, p, and d Block Elements — A/L Chemistry

How do I practise Chemistry of s, p, and d Block Elements?

1 question with a worked solution

Check before you answer: Group Trends (s & p blocks): Explaining periodic variation in atomic radii, ionization energies, electronegativity, flame test colors, and thermal decomposition of nitrates and carbonates.

1. Which statement correctly explains why aqueous solutions of [Ti(H₂O)₆]³⁺ are violet in color, whereas aqueous solutions of [Sc(H₂O)₆]³⁺ are colorless?
   1. A) Sc³⁺ is paramagnetic, while Ti³⁺ is diamagnetic in aqueous solution
   2. B) Ti³⁺ has a 3d¹ configuration allowing d-d electronic transitions in visible light, while Sc³⁺ has a 3d⁰ configuration with no d-electrons
   3. C) Sc³⁺ undergoes charge transfer transitions in the infrared region, whereas Ti³⁺ does not
   4. D) Ti³⁺ forms a tetrahedral complex, whereas Sc³⁺ forms an octahedral complex
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   Correct answer: B) Ti³⁺ has a 3d¹ configuration allowing d-d electronic transitions in visible light, while Sc³⁺ has a 3d⁰ configuration with no d-electrons

   Titanium (atomic number 22) has ground state configuration [Ar] 3d² 4s². For Ti³⁺, the configuration is [Ar] 3d¹. In an octahedral crystal field, the d-orbitals split into t₂g and e_g levels. Absorption of visible light promotes the single 3d electron from t₂g to e_g (d-d transition), resulting in a violet transmitted color. Scandium (atomic number 21) has configuration [Ar] 3d¹ 4s²; Sc³⁺ is [Ar] 3d⁰, possessing no d-electrons, so d-d transitions are impossible and the complex is colorless.

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   Step 1: Write electronic configurations for the central ions: Ti: [Ar] 3d² 4s² → Ti³⁺: [Ar] 3d¹ (one d-electron). Sc: [Ar] 3d¹ 4s² → Sc³⁺: [Ar] 3d⁰ (empty d-subshell). Step 2: Consider crystal field splitting: in an octahedral field of water ligands, 3d splits into t₂g and e_g levels. Step 3: For Ti³⁺, the energy difference Δ_oct corresponds to green-yellow wavelengths in visible spectrum; absorbing green-yellow transmits the complementary violet color. Step 4: For Sc³⁺, with zero d-electrons, no d-d transition can occur, so no visible light is absorbed. Answer: Ti³⁺ has a 3d¹ configuration allowing d-d electronic transitions in visible light, while Sc³⁺ has a 3d⁰ configuration with no d-electrons.
   Modelled on: the A/L Chemistry examination pattern

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Where does Chemistry of s, p, and d Block Elements fit in the syllabus?

Grade 12 · Term 2