JEE Main Chemistry · d & f Block Elements PYQ
JEE Main d- and f-Block Elements PYQ (2002–2025)
d- and f-Block Elements is a P2 Inorganic Chemistry chapter — ~4% JEE Main weightage with 1–2 questions per session. Focus is on transition metal properties, lanthanide contraction, actinoid chemistry and the manufacture and properties of KMnO₄ and K₂Cr₂O₇.
d- and f-Block PYQs from 2002 to 2025 with every solution citing NCERT Class 12 Chapter 8 references for trend questions and reaction-scheme diagrams for compound preparation questions.
d- and f-Block Elements at a Glance
Key Sub-Topics & What's Tested
General Properties of Transition Metals
Variable oxidation states, formation of coloured ions, paramagnetism, catalytic activity, interstitial compounds, alloy formation.
Electronic Configuration Trends
d-block configurations, anomalies (Cr: 3d⁵4s¹, Cu: 3d¹⁰4s¹), stability of half-filled and fully-filled d-orbitals.
Oxidation State Variations
Multiple oxidation states across transition series, maximum state reached by Mn (+7), stabilisation of higher states in oxides and fluorides.
Ionisation Enthalpies
Trends down the group (generally decrease) and across the period (irregular), comparison with s-block and p-block elements.
Metallic Character & Atomic Radii
Similar atomic radii in a period due to d-contraction, lanthanide contraction's effect on 5d/4d series, why Hf and Zr have nearly equal radii.
Coloured Compounds
d-d transitions in partially filled d-orbitals, charge transfer complexes (CT bands), Zn²⁺, Cu⁺ are colourless (completely filled or empty d).
Important Compounds
KMnO₄ preparation (from pyrolusite MnO₂), K₂Cr₂O₇ preparation (from chromite FeCr₂O₄), redox reactions with these oxidants.
Lanthanide & Actinoid Chemistry
Lanthanide contraction (cause and consequences), common oxidation states (Ln: mostly +3), actinoids' radioactivity, Hg's unique behaviour.
Question Type Distribution
| Question Type | Share (approx) | Example Pattern |
|---|---|---|
| Electronic Configuration | 20% | Write electronic configuration of Cu²⁺ and predict its magnetic behaviour. |
| Oxidation State Identification | 20% | What is the oxidation state of Cr in K₂Cr₂O₇? Why does Mn show +7 state but Fe doesn't? |
| Colour Explanation | 15% | Why is [Zn(H₂O)₆]²⁺ colourless while [Cu(H₂O)₆]²⁺ is blue? |
| Lanthanide Contraction Effect | 15% | Why do Zr and Hf have almost identical atomic radii? |
| KMnO₄ / K₂Cr₂O₇ Reactions | 15% | Products when KMnO₄ reacts with Fe²⁺ in acidic medium. |
| Magnetic Moment | 15% | Calculate spin-only magnetic moment of Fe³⁺ given 5 unpaired electrons. |
How to Solve d- and f-Block Elements PYQs
- 1Know Cr and Cu anomalous configurations. Cr: [Ar] 3d⁵ 4s¹ (half-filled d stability). Cu: [Ar] 3d¹⁰ 4s¹ (full d stability). These are predictable exceptions.
- 2Colour = partially filled d-orbitals. d⁰ (Sc³⁺, Ti⁴⁺) and d¹⁰ (Zn²⁺, Cu⁺) are colourless. d¹ to d⁹ are generally coloured due to d-d transitions.
- 3Lanthanide contraction: memorise effects. Similar Zr/Hf radii, higher densities of 5d elements, basicity of lanthanide hydroxides decreases, ionic radii decrease down Ln series.
- 4KMnO₄ redox behaviour: medium-dependent. In acid: MnO₄⁻ → Mn²⁺ (n=5). In neutral: MnO₄⁻ → MnO₂ (n=3). In basic: MnO₄⁻ → MnO₄²⁻ (n=1). Pick n based on medium.
- 5K₂Cr₂O₇: in acid medium only. Cr₂O₇²⁻ → Cr³⁺ with n=6 electrons. Always works in acidic conditions. Use for iron titrations, SO₂ tests.
Common Mistakes That Cost Marks
- Forgetting (n-1)d before ns in configurations. Correct order for writing: 4s before 3d during filling, but (n-1)d before ns once electrons are in. So Fe²⁺ = [Ar] 3d⁶ (remove 4s first, then 3d).
- Expecting all d-block elements to be coloured. Sc³⁺ (3d⁰) and Zn²⁺ (3d¹⁰) are colourless despite being d-block. Configuration matters, not group membership.
- Confusing lanthanide contraction with d-contraction. Lanthanide contraction is across 4f series. d-contraction is across 3d, 4d, 5d series. Different phenomena.
- Wrong n for KMnO₄. Using n=3 (neutral) in acidic problem or n=5 (acid) in basic problem. Always identify medium first.
- Calling actinoids f-block trivia. Actinoids show variable oxidation states unlike lanthanides (mostly +3). U commonly shows +6 (UO₂²⁺), Pu shows multiple states. More chemistry than lanthanides.
Related JEE Main Practice
Frequently asked questions
How many d- and f-Block PYQs should I solve?
Target 40–60 PYQs across 2010–2025. Given P2 status (4% weightage), practice volume is moderate but NCERT recall is key.
Is NCERT Class 12 Chapter 8 enough?
Yes — NCERT Ch 8 (d- and f-Block) covers this chapter comprehensively. Add KMnO₄/K₂Cr₂O₇ preparation diagrams from NCERT for PYQ-ready recall.
What's the most-tested d-Block PYQ pattern?
Electronic configuration and oxidation state identification. Appears in ~6 PYQs per 10-year window. Know the series: Sc to Zn, Y to Cd, La to Hg.
Do I need to know lanthanide/actinoid chemistry in detail?
For lanthanides: know contraction, +3 as dominant state, chemical similarity. For actinoids: know radioactivity, multiple oxidation states, uranium chemistry briefly. Don't over-study.
Why does Zn²⁺ show no colour?
Zn²⁺ has 3d¹⁰ configuration (all d-orbitals filled). No d-d transition possible → no visible light absorption → appears colourless. Key test for understanding d-d transitions.
Does this connect with Coordination Compounds?
Yes directly — transition metal centres form the core of most coordination compounds. Magnetic moment, hybridisation, geometry concepts carry over entirely.
Start d- and f-Block PYQs free
P2 Inorganic chapter. Chapter-wise PYQs on transition metals, lanthanide contraction and KMnO₄/K₂Cr₂O₇. Sign in in 30 seconds.
Start Free Practice