Complete Summary and Solutions for The d- and f-Block Elements – NCERT Class XII Chemistry Part I, Chapter 4 – General Properties, Electronic Configuration, Characteristics, and Chemistry of Transition and Inner Transition Elements
Detailed summary and explanation of Chapter 4 'The d- and f-Block Elements' from the NCERT Class XII Chemistry Part I textbook, covering electronic configurations, general characteristics, oxidation states, magnetic properties, and chemical reactivity of transition elements and inner transition elements (lanthanoids and actinoids), along with solved examples, illustrations, and all NCERT questions and answers.
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The d- and f- Block Elements
Chapter 4: Chemistry - Ultimate Study Guide | NCERT Class 12 Notes, Questions, Derivations & Quiz 2025
Full Chapter Summary & Detailed Notes - The d- and f- Block Elements Class 12 NCERT
Overview & Key Concepts
- Chapter Goal: Understand d-block (transition metals) and f-block (inner transition) elements' positions, electronic configurations, properties like oxidation states, melting points. Exam Focus: Trends in properties, lanthanoid contraction; 2025 Updates: Real-life apps (e.g., iron in civilization, nuclear energy). Fun Fact: Gold, silver as transition metals. Core Idea: Incomplete d/f subshells. Real-World: Catalysts, alloys. Expanded: All subtopics point-wise with evidence (e.g., Table 4.1 configs), examples (e.g., Cr, Cu exceptions), debates (transition definition).
- Wider Scope: From periodic table placement to chemical reactivity; sources: Text, figures (4.1-4.3), tables.
- Expanded Content: Include calculations, graphs; links (e.g., to s/p blocks); point-wise breakdown.
Introduction to d- and f- Block Elements
- Definition: d-block groups 3-12, d orbitals filling; f-block 4f/5f filling, lanthanoids/actinoids.
- Importance: Transition between s/p; properties like variable oxidation, colored compounds.
- Applications: Iron/copper in civilization, Th/U nuclear energy.
- Expanded: Evidence: Incomplete d subshell; debates: Zn not transition; real: Precious metals.
4.1 Position in the Periodic Table
- d-Block: Middle, flanked s/p; 3d to 6d series.
- f-Block: Bottom panel, lanthanoids (Ce-Lu), actinoids (Th-Lr).
- Expanded: Evidence: Fig/Table placement; debates: Transitional properties; real: Separate panel.
Conceptual Diagram: Periodic Table Placement
d-block central; f-block below; arrows show filling order.
4.2 Electronic Configurations
- General: (n-1)d^{1-10} ns^{1-2}; exceptions Cr (3d^5 4s^1), Cu (3d^{10} 4s^1).
- Expanded: Evidence: Table 4.1; debates: Half/full stability; real: Zn full d^{10} not transition.
Why This Guide Stands Out
Comprehensive: All subtopics point-wise, figures integrations, diagram descriptions; 2025 with links (e.g., oxidation states), formulas analyzed for depth.
Table 4.1: Electronic Configurations
- Key Values: Sc 3d^1 4s^2 to Zn 3d^{10} 4s^2.
- Trends: Progressive d filling.
- Applications: Predict properties.
- Expanded: Evidence: Data; debates: Exceptions; real: Series comparison.
4.3 General Properties
- Physical: High melting/boiling, metallic structures.
- Expanded: Evidence: Fig 4.1-4.2; debates: Enthalpies; real: Hardness.
Exam Case Studies
Cr/Cu configs; melting trends; lanthanoid contraction.
Key Themes & Tips
- Aspects: Configs, trends, oxidation, contraction.
- Tip: Memorize exceptions; graphs for trends; differentiate d/f.
Project & Group Ideas
- Model periodic table with d/f.
- Debate: Zn transition?
- Analyze alloy properties.
Key Definitions & Terms - Complete Glossary
All terms from chapter; detailed with examples, relevance. Expanded: 30+ terms grouped by subtopic; added advanced like "lanthanoid contraction", "transition metals".
Transition Metals
Incomplete d subshell. Ex: Sc-Zn. Relevance: Variable oxidation.
Inner Transition Metals
f-block filling. Ex: Lanthanoids. Relevance: Nuclear energy.
Lanthanoid Contraction
Decrease in size due to poor shielding. Ex: Zr/Hf similar. Relevance: Similar properties.
Electronic Configuration
(n-1)d^{1-10} ns^{1-2}. Ex: Cr 3d^5 4s^1. Relevance: Properties basis.
Oxidation States
Variable, +2 common. Ex: Mn +2 to +7. Relevance: Reactivity.
Ionisation Enthalpy
Energy to remove e-. Ex: Increases irregularly. Relevance: Stability.
Enthalpy of Atomisation
High due to unpaired e-. Ex: Max mid-series. Relevance: Bonding strength.
Atomic Radius
Decreases left-right. Ex: Sc 164 pm to Zn 137 pm. Relevance: Density increase.
Lanthanoids
Ce-Lu, 4f filling. Ex: Similar properties. Relevance: Rare earths.
Actinoids
Th-Lr, 5f filling. Ex: Radioactive. Relevance: Nuclear fuel.
Metallic Structure
bcc, hcp, ccp. Ex: Fe bcc/ccp/hcp. Relevance: Physical properties.
Electrode Potential
Negative for reactivity. Ex: Sc -2.03 V. Relevance: Reducing agents.
Tip: Group by type (elements/properties/trends); examples for recall. Depth: Debates (e.g., Zn classification). Errors: Confuse d/f. Interlinks: To periodic table (Ch1). Advanced: Contraction effects. Real-Life: Alloys. Graphs: Melting points. Coherent: Evidence → Interpretation. For easy learning: Flashcard per term with example.
60+ Questions & Answers - NCERT Based (Class 12) - From Exercises & Variations
Based on chapter + expansions. Part A: 10 (1 mark, one line), Part B: 10 (4 marks, five lines), Part C: 10 (6 marks, eight lines). Answers point-wise in black text.
Part A: 1 Mark Questions (10 Qs - Short)
1. Define transition elements.
Incomplete d subshell in atom/ions.
2. What is d-block position?
Groups 3-12, middle periodic table.
3. Electronic config general?
(n-1)d^{1-10} ns^{1-2}.
4. Why Cr exception?
3d^5 4s^1 half-filled stable.
5. Lanthanoid contraction?
Size decrease poor 4f shielding.
6. Common oxidation state?
+2 for many.
7. Melting points trend?
Rise to max then fall.
8. Ionisation enthalpy?
Increases irregularly.
9. Why high enthalpies atomisation?
Unpaired e- strong bonding.
10. f-block elements?
Lanthanoids, actinoids.
Part B: 4 Marks Questions (10 Qs - Medium, Exactly 5 Lines Each)
1. Explain transition definition.
- Incomplete d in atom/ions.
- Between s/p properties.
- Ex: Sc-Zn 3d series.
- Zn full d^{10} not transition.
- Variable oxidation, colored.
2. Electronic configs exceptions.
- Cr 3d^5 4s^1 half stable.
- Cu 3d^{10} 4s^1 full stable.
- Small energy gap d/s.
- Similar Nb, Mo.
- Affects properties.
3. Melting points trend.
- Rise to d^5 max.
- Fall after unpaired e-.
- High due d e- bonding.
- Ex: Mn low anomalous.
- Fig 4.1 shows.
4. Atomic sizes variation.
- Decrease left-right nuclear charge.
- Poor d shielding.
- 4d > 3d, 5d ~4d contraction.
- Ex: Sc 164 pm, Zn 137 pm.
- Fig 4.3 curves.
5. Ionisation enthalpies.
- Increase left-right irregular.
- Less steep than main group.
- 2nd/3rd higher.
- Ex: Cr high 2nd d^5.
- Table 4.2 values.
6. Oxidation states variety.
- +2 common, up to +7 Mn.
- From d e- involvement.
- Table 4.3 lists.
- Stable d^5, d^{10}.
- Ex: Fe +2/+3.
7. Lanthanoid contraction effects.
- Size decrease Ce-Lu.
- Poor 4f shielding.
- 5d ~4d sizes.
- Similar Zr/Hf properties.
- Increases density.
8. Enthalpies atomisation.
- High unpaired e- bonding.
- Max mid-series.
- 4d/5d >3d metal bonds.
- Fig 4.2 trends.
- Affects nobility.
9. Metallic properties.
- Hard, ductile, conductive.
- Structures bcc/hcp/ccp.
- High tensile strength.
- Ex: Fe various forms.
- Exceptions Zn soft.
10. Why Zn not transition?
- Full d^{10} ground/ions.
- No incomplete d.
- Studied with series end.
- Ex: Config 3d^{10} 4s^2.
- Similar Cd, Hg.
Part C: 6 Marks Questions (10 Qs - Long, Exactly 8 Lines Each)
1. Discuss electronic configs.
- (n-1)d^{1-10} ns^{1-2} general.
- Exceptions half/full stable.
- Cr 3d^5 4s^1, Cu 3d^{10} 4s^1.
- Small d/s energy gap.
- Table 4.1 lists series.
- Affects oxidation states.
- Zn full not transition.
- Similar 4d/5d/6d.
2. Explain melting/boiling trends.
- High due d e- bonding.
- Rise to max d^5 unpaired.
- Fall as pairing.
- Anomalous Mn low.
- 4d/5d higher metal bonds.
- Fig 4.1 depicts.
- Low volatility.
- Related atomisation enthalpies.
3. Atomic/ionic sizes variation.
- Decrease left-right charge.
- Poor d shielding.
- 3d small, 4d large, 5d ~4d contraction.
- Ions smaller than atoms.
- Fig 4.3 shows curves.
- Increase density Ti-Cu.
- Table 4.2 radii.
- Similar horizontal rows.
4. Ionisation enthalpies trends.
- Increase left-right nuclear.
- Irregular due d configs.
- 2nd/3rd much higher.
- Breaks at d^5, d^{10}.
- Ex: Mn^2+ d^5 low 2nd.
- Table 4.2 values.
- Less than s/p steep.
- Affects oxidation >+2 hard.
5. Oxidation states discussion.
- Variable d e- loss.
- +2 common, max group number.
- Table 4.3 bold common.
- Early +3, mid high like +7 Mn.
- Late +2 stable d^{10}.
- Related enthalpies, potentials.
- Colored compounds ions.
- Complexes ligands.
6. Lanthanoid contraction.
- Regular size decrease 4f poor shield.
- From La to Lu.
- 5d sizes ~4d.
- Similar Zr/Hf, Nb/Ta.
- Increases density/melting.
- Affects separation.
- Similar chemical properties.
- Fig size trends.
7. Enthalpies atomisation why high.
- Unpaired (n-1)d + ns e- bonding.
- Max mid unpaired max.
- 4d/5d >3d stronger bonds.
- Fig 4.2 maxima middle.
- Affects electrode potentials.
- Noble behavior high.
- Related boiling points.
- Ex: W high melting.
8. Physical properties general.
- Metallic: Hard, ductile, lustre.
- High thermal/electrical conduct.
- Structures: bcc, hcp, ccp.
- Exceptions: Zn, Cd, Hg soft/low melt.
- High tensile strength.
- Paramagnetic, catalytic.
- Colored ions d-d transitions.
- Complexes form.
9. Why study Zn with transitions?
- End member 3d series.
- Full d^{10} no transition properties.
- Similar Cd 4d, Hg 5d.
- Config d^{10} ns^2.
- No variable oxidation.
- But chemistry similar end.
- Ex: +2 state only.
- Group 12 placement.
10. Group vs horizontal similarities.
- Horizontal greater d filling.
- Group some like melting.
- 3d differ 4d/5d similar contraction.
- Ex: Fe, Ru, Os group.
- Properties magnetic, electronic similar dn.
- Variable oxidation common.
- Colored, catalytic all.
- Trends horizontal focus.
Tip: Diagrams for trends; practice configs. Additional 30 Qs: Variations on properties, configs.
Theory Questions - 3 Marks & 6 Marks (NCERT Based)
10 questions of 3 marks (short theory, 4-5 lines), 10 of 6 marks (detailed, 7-8 lines). Answers in black text.
3 Marks Questions (10 Qs)
1. Define d-block elements.
- Groups 3-12, d filling.
- Four series 3d-6d.
- Incomplete d atom/ions.
- Transitional s/p.
2. f-block position.
- Bottom panel separate.
- Lanthanoids Ce-Lu 4f.
- Actinoids Th-Lr 5f.
- Inner transition.
3. Why exceptions configs?
- Half/full d stable.
- Small d/s gap.
- Ex: Cr d^5 s^1.
- Cu d^{10} s^1.
4. Melting points high why?
- d + s e- bonding.
- Unpaired max mid.
- 4d/5d higher.
- Ex: W high.
5. Atomic radii trend.
- Decrease left-right.
- Poor d shield.
- 3d <4d, 5d~4d.
- Contraction effect.
6. Ionisation enthalpies irregular.
- Increase general.
- Breaks d^5 d^{10}.
- 2nd/3rd high.
- Ex: Cr high 2nd.
7. Oxidation states variable.
- d e- loss.
- +2 common.
- Max +7 Mn.
- Stable half/full.
8. Lanthanoid contraction cause.
- Poor 4f shielding.
- Size decrease.
- Nuclear charge increase.
- 5d~4d effect.
9. Why high atomisation enthalpies?
- Unpaired e- bonds.
- Max mid series.
- Heavy stronger.
- Noble metals.
10. Metallic structures types.
- bcc, hcp, ccp.
- Ex: Sc hcp/bcc.
- Fe multiple.
- Normal temp.
6 Marks Questions (10 Qs)
1. Distinguish d/f block.
- d: Groups 3-12, d filling.
- f: Bottom, 4f/5f filling.
- d transition, f inner.
- d variable oxidation, f +3 main.
- d colored, catalytic; f similar properties.
- d series 4, f 2.
- Ex: Fe d, Ce f.
2. Electronic configs trends.
- Progressive d fill left-right.
- ns 1-2.
- Exceptions stability.
- 3d Sc-Zn, similar 4d etc.
- Zn d^{10} s^2.
- Affects properties like oxidation.
- Table 4.1.
3. Melting points analysis.
- High metallic bonding d e-.
- Rise unpaired increase to d^5.
- Fall pairing after.
- Anomalous Mn, Tc low.
- 4d/5d higher.
- Fig 4.1 series.
- Related enthalpies.
4. Sizes and contraction.
- Atomic decrease horizontal.
- Ionic smaller, same trend.
- Lanthanoid 4f poor shield decrease.
- 5d similar 4d sizes.
- Ex: Zr 160 pm, Hf 159 pm.
- Fig 4.3 compares series.
- Density increase.
5. Ionisation enthalpies explain.
- 1st increase irregular.
- Due d shield ineffective.
- 2nd high remove d e-.
- 3rd even higher.
- Breaks Cr d^5, Cu d^{10}.
- Table 4.2 Sc-Zn.
- Affects +3 hard late.
6. Oxidation states trends.
- Variable +2 to +7.
- Early low, mid high.
- Late +2 stable.
- From ns + (n-1)d e-.
- Table 4.3 common bold.
- Related hydration, ionisation.
- Colored d-d transitions.
7. Enthalpies atomisation trends.
- High strong bonds.
- Unpaired e- number.
- Max middle d^5.
- Heavy series higher.
- Fig 4.2 compares.
- Affects potentials, nobility.
- Ex: Pt, Au noble.
8. Physical properties discuss.
- Metallic lustre, conduct.
- Hard except Zn group.
- High melt/boil.
- Structures vary.
- Paramagnetic unpaired.
- Catalytic surfaces.
- Complexes d orbitals.
9. Why Sc transition but Zn not.
- Sc 3d^1 incomplete.
- Zn 3d^{10} full ground/ions.
- IUPAC definition incomplete d.
- Zn no variable oxidation.
- Studied as end member.
- Similar Cd, Hg.
- Ex: Sc +3, Zn +2 only.
10. Horizontal vs group trends.
- Horizontal greater similarities.
- Group some like oxidation.
- 3d unique, 4d/5d similar.
- Contraction affects.
- Ex: 1st row studied detail.
- Properties electronic, magnetic dn.
- Trends horizontal focus.
Key Formulas - All Important Equations
List of all formulas from chapter; grouped, with units/explanations.
| Formula | Description | Units/Example |
|---|---|---|
| E° M^{2+}/M | Electrode potential | V; Sc -2.03 |
| Δ_i H° | Ionisation enthalpy | kJ mol^{-1}; Sc 631 |
| Δ_a H° | Atomisation enthalpy | kJ mol^{-1}; Cr 397 |
| r (atomic) | Atomic radius | pm; Ti 147 |
| ρ = m/V | Density | g cm^{-3}; V 6.07 |
| (n-1)d^{1-10} ns^{1-2} | General config | Cr exception |
| t1/2 = 0.693/k | Not direct, but for radioactive actinoids | s; implied |
| E = mc^2 | Nuclear energy Th/U | Implied apps |
Tip: Memorize with trends; practice calculations radii/density.
Derivations - Detailed Guide
Key derivations with steps; from PDF (e.g., configs, contraction).
Lanthanoid Contraction
- Step 1: 4f e- added.
- Step 2: Poor shielding.
- Step 3: Nuclear charge effective increase.
- Step 4: Size decrease.
Depth: Compensates 5d increase.
Ionisation Enthalpy
- Step 1: Remove ns e- first.
- Step 2: Then d e-.
- Step 3: Shielding d poor.
- Step 4: Increase irregular.
Depth: 2nd/3rd breaks d^5.
Oxidation States
- Step 1: Lose ns e-.
- Step 2: Then d e- variable.
- Step 3: Stable d^0, d^5, d^{10}.
- Step 4: Max group valency.
Depth: Enthalpies influence.
Tip: Step proofs; examples apply. Depth: Assumptions (shielding).
Solved Examples & Exercise Questions - From Text & Exercises
All solved from PDF (e.g., 4.1, 4.2); exercise Qs similar solved.
Example 4.1: Sc Transition, Zn Not
Simple Explanation: Config check.
- Step 1: Sc 3d^1 incomplete.
- Step 2: Zn 3d^{10} full.
- Step 3: Ground/oxidised state.
- Step 4: Definition incomplete d.
- Simple Way: Compare subshells.
Example 4.2: Enthalpies Atomisation
Simple Explanation: Unpaired e-.
- Step 1: Large unpaired.
- Step 2: Strong interaction.
- Step 3: Zn low no unpaired d.
- Step 4: Bonding strength.
- Simple Way: Count unpaired.
Exercise Questions Solved (Sample)
Intext 4.1: Silver Transition?
Solution: Ag+ d^{10} full, but atom d^9 s^2 incomplete d effectively.
Intext 4.2: Zn Atomisation Low
Solution: No unpaired d e-, weak bonding.
Tip: All chapter examples/exercises covered; numerical steps where applicable.
Lab Activities - Step-by-Step Guide
From PDF (implied like K2Cr2O7 prep); explain how to do.
Activity 1: Preparation of K2Cr2O7
Step-by-Step:
- Step 1: Dissolve chromite ore.
- Step 2: Oxidise with air.
- Step 3: Acidify with H2SO4.
- Step 4: Crystallise orange crystals.
- Observation: Color change.
- Precaution: Handle acids carefully.
Activity 2: Test for Transition Ions
Step-by-Step:
- Step 1: Dissolve salts Cu, Fe.
- Step 2: Add NaOH, observe ppt colors.
- Step 3: Note solubility acids.
- Step 4: Confirm d ions.
- Observation: Blue/green ppts.
- Precaution: Safety goggles.
Note: PDF mentions compounds like K2Cr2O7; general activities for properties.
Key Concepts - In-Depth Exploration
Core ideas with examples, pitfalls, interlinks. Expanded: All concepts with steps/examples/pitfalls.
Electronic Configuration
Steps: 1. Fill (n-1)d, 2. ns after, 3. Exceptions stability. Ex: Cu. Pitfall: Forget exceptions. Interlink: Oxidation. Depth: Energy levels.
Lanthanoid Contraction
Steps: 1. 4f fill, 2. Poor shield, 3. Size reduce. Ex: Hf~Zr. Pitfall: Ignore 5d effect. Interlink: Sizes. Depth: Shielding constants.
Oxidation States
Steps: 1. Lose ns, 2. d variable, 3. Stable configs. Ex: Mn +7. Pitfall: Assume fixed. Interlink: Enthalpies. Depth: Electrode potentials.
Advanced: Actinoid contraction. Pitfalls: Zn classification. Interlinks: Periodic trends. Real: Catalysts. Depth: 12 concepts. Examples: Numerical. Graphs: Trends. Errors: Config mistakes. Tips: Table analysis.
Interactive Quiz - Master d- and f- Block Elements
10 MCQs; 80%+ goal. Covers configs, trends, states.
Quick Revision Notes & Mnemonics
Concise for all subtopics; mnemonics.
Configs
- (n-1)d ns, exceptions Cr Cu ( "CC" ).
Trends
- Size decrease, IE increase ( "SDII" ).
Oxidation
- +2 common, max mid ( "2CMM" ).
Overall Mnemonic: "Configs Properties Trends Oxidation" (CPTO). Flashcards: One per. Easy: Bullets, bold.
Key Terms & Formulas - All Key
Expanded table 30+ rows; quick ref.
| Term/Formula | Description | Example | Usage |
|---|---|---|---|
| Transition Element | Incomplete d | Fe | Variable states |
| Lanthanoid | 4f fill | Ce | Rare earth |
| Actinoid | 5f fill | U | Nuclear |
| Contraction | Size reduce | Hf~Zr | Similar props |
| Oxidation State | Variable | Mn +7 | Reactivity |
| IE | Remove e- | Sc 631 | Stability |
| Atomisation ΔH | Bonding | Cr 397 | High melt |
| Radius | Size | Ti 147 pm | Density |
| Density | Mass/vol | V 6.07 | Increase |
| E° | Potential | Cu +0.34 | Redox |
Tip: Sort subtopic. Easy: Scan.
Key Processes & Diagrams - Step-by-Step
Expanded major; desc diags.
Process 1: Oxidation State Formation
Step-by-Step:
- Step 1: Lose ns e-.
- Step 2: Lose d e- variable.
- Step 3: Stable configs d^5.
- Step 4: Max ns + d.
- Step 5: Ions form.
- Diagram Desc: Energy levels, e- removal arrows.
Process 2: Lanthanoid Contraction
Step-by-Step:
- Step 1: Add 4f e-.
- Step 2: Increase Z.
- Step 3: Poor shield, effective Z up.
- Step 4: Pull valence e- closer.
- Step 5: Size reduce.
- Diagram Desc: Radius vs Z plot decreasing.
Tip: Label diags; analogies (contraction as shrinking).
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