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Inorganic Chemistry XII · 2 Chapters · 14 marks

Inorganic Chemistry Formula Reference

d & f Block Elements and Coordination Compounds — key equations, reactions and relationships.

⚡ Critical Facts — Memorise These First

Magnetic Momentμ = √n(n+2) BM
KMnO₄ (acidic)MnO₄⁻ + 8H⁺ + 5e⁻ → Mn²⁺
K₂Cr₂O₇ (acidic)Cr₂O₇²⁻ + 14H⁺ + 6e⁻ → 2Cr³⁺
CFSE (oct.)−0.4n(t2g) + 0.6n(eg) × Δo
Cr exception[Ar] 3d⁵ 4s¹
Cu exception[Ar] 3d¹⁰ 4s¹
Δt vs ΔoΔt ≈ (4/9) Δo
Lanthanoid contractionLa³⁺ 106 pm → Lu³⁺ 86 pm
04 d & f Block Elements 7 marks
d-block Configuration
General: (n−1)d¹⁻¹⁰ ns⁰⁻²
Exceptions: Cr = [Ar] 3d⁵ 4s¹ ; Cu = [Ar] 3d¹⁰ 4s¹ (half/fully filled stability).
KMnO₄ — Acidic Medium
MnO₄⁻ + 8H⁺ + 5e⁻ → Mn²⁺ + 4H₂O
Gains 5e⁻ (Mn: +7 → +2). Pink/violet → colourless. E° = +1.51 V. Oxidises Fe²⁺, oxalic acid, SO₂.
KMnO₄ — Neutral/Faintly Alkaline
MnO₄⁻ + 2H₂O + 3e⁻ → MnO₂ + 4OH⁻
Gains 3e⁻ (Mn: +7 → +4). Brown/black precipitate of MnO₂ formed.
K₂Cr₂O₇ — Acidic Medium
Cr₂O₇²⁻ + 14H⁺ + 6e⁻ → 2Cr³⁺ + 7H₂O
Gains 6e⁻ (Cr: +6 → +3). Orange → green. E° = +1.33 V. Oxidises Fe²⁺, I⁻, H₂S.
Chromate-Dichromate Equilibrium
Cr₂O₇²⁻ + H₂O ⇌ 2CrO₄²⁻ + 2H⁺
Yellow (chromate, basic) ⇌ Orange (dichromate, acidic). Equilibrium shifts with pH.
Lanthanoid Contraction
Ionic radii: La³⁺ (106 pm) → Lu³⁺ (86 pm)
Steady decrease across lanthanoids due to poor shielding by 4f electrons. Causes atomic radii of 5d ≈ 4d elements.
05 Coordination Compounds 7 marks
Magnetic Moment
μ = √(n(n+2)) BM
n = number of unpaired electrons. 1 unpaired e⁻ → μ ≈ 1.73 BM; 5 unpaired → μ ≈ 5.92 BM.
Crystal Field Splitting (Octahedral)
Δo = energy gap between eg and t2g CFSE = −0.4n(t2g) × Δo + 0.6n(eg) × Δo
t2g (lower) has 3 orbitals; eg (higher) has 2. Strong field → large Δo → low spin. Weak field → small Δo → high spin.
Octahedral vs Tetrahedral Δ
Δt ≈ (4/9) Δo
Tetrahedral splitting is always smaller → most tetrahedral complexes are high-spin.
Spectrochemical Series (weak → strong field)
I⁻ < Br⁻ < SCN⁻ < Cl⁻ < S²⁻ < F⁻ < OH⁻ < C₂O₄²⁻ < H₂O < NCS⁻ < NH₃ < en < NO₂⁻ < CN⁻ < CO
Strong field ligands (CN⁻, CO, NO₂⁻) → large Δo → low spin → paired electrons. Weak field (I⁻, Br⁻, Cl⁻) → small Δo → high spin → unpaired electrons. H₂O is the reference mid-field ligand.
IUPAC Naming Rules
[Ligands (alphabetical) Metal(ox.state)]^charge
Cation named before anion. Ligands: aqua, ammine, chlorido, cyano, oxido. Metal with −ate suffix if in anionic complex.