Science · Class 12
d and f Block Elements
Learn d and f Block Elements with notes, examples, and practice questions.
4 sections15–25 min read6 MCQs · 2 examples
Chapter Overview
d-block (transition metals) and f-block (lanthanoids/actinoids) elements show coloured ions, variable oxidation states, catalytic behaviour, and magnetic properties.
Transition Metals (3d series)
- Partially filled d orbitals
- Variable oxidation states (Mn: +2 to +7)
- Coloured compounds — d-d transitions
- Paramagnetic when unpaired electrons
- Form complexes and alloys
Important Compounds
- KMnO₄: strong oxidising agent (purple)
- K₂Cr₂O₇: orange oxidiser in acidic medium
- CuSO₄·5H₂O: blue vitriol
- Fe: rusting, haemoglobin
f-Block
- Lanthanoids: +3 common; lanthanoid contraction
- Actinoids: radioactive; variable valency
- 4f and 5f electron filling
Solved Examples
Step-by-step solutions — read each step before checking the final answer.
Oxidation state
KMnO₄: O is −2, K is +1. Mn?
- 1+1+Mn+4(−2)=0
- 2Mn=+7
Answer
+7
Colour
Why Cu²⁺ aqueous is blue?
- 1d-d transition absorbs red, transmits blue
Answer
Incomplete d subshell transitions
Key Points to Remember
- ✓ Zn, Cd, Hg: d¹⁰ — not typical transition properties
- ✓ Interstitial compounds: small atoms in metal lattice
- ✓ Catalysis by d metals (Ni, Pt)
Exam Tips
- • Balancing permanganate in acidic medium
- • Compare 3d vs 4d vs 5d trends
- • Lanthanoid contraction effect on size
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Formula Cheat Sheet
Quick reference — NCERT board exam formulas
Transition & f-Block
- Transition metals: partially filled d orbitals
- KMnO₄:Mn oxidation state = +7
- K₂Cr₂O₇:Cr oxidation state = +6
- Colour: d-d transitions (unpaired e⁻)
- Lanthanoid contraction: gradual decrease in 4f series size
- Zn²⁺ colourless: d¹⁰ (no d-d transition)
Practice MCQs — d and f Block Elements
Test your understanding with topic-wise multiple choice questions. Explanations appear after each answer.
Question 1 of 6Score: 0/0
Transition elements have: