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.
Updated: 4 months ago
Categories: NCERT, Class XII, Chemistry Part I, Chapter 4, d-Block Elements, f-Block Elements, Transition Elements, Inner Transition Elements, Summary, Questions, Answers
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.
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.
1 Mark Answer:
Incomplete d subshell in atom/ions.
2. What is d-block position?
1 Mark Answer:
Groups 3-12, middle periodic table.
3. Electronic config general?
1 Mark Answer:
(n-1)d^{1-10} ns^{1-2}.
4. Why Cr exception?
1 Mark Answer:
3d^5 4s^1 half-filled stable.
5. Lanthanoid contraction?
1 Mark Answer:
Size decrease poor 4f shielding.
6. Common oxidation state?
1 Mark Answer:
+2 for many.
7. Melting points trend?
1 Mark Answer:
Rise to max then fall.
8. Ionisation enthalpy?
1 Mark Answer:
Increases irregularly.
9. Why high enthalpies atomisation?
1 Mark Answer:
Unpaired e- strong bonding.
10. f-block elements?
1 Mark Answer:
Lanthanoids, actinoids.
Part B: 4 Marks Questions (10 Qs - Medium, Exactly 5 Lines Each)
1. Explain transition definition.
4 Marks Answer:
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.
4 Marks Answer:
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.
4 Marks Answer:
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.
4 Marks Answer:
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.
4 Marks Answer:
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.
4 Marks Answer:
+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.
4 Marks Answer:
Size decrease Ce-Lu.
Poor 4f shielding.
5d ~4d sizes.
Similar Zr/Hf properties.
Increases density.
8. Enthalpies atomisation.
4 Marks Answer:
High unpaired e- bonding.
Max mid-series.
4d/5d >3d metal bonds.
Fig 4.2 trends.
Affects nobility.
9. Metallic properties.
4 Marks Answer:
Hard, ductile, conductive.
Structures bcc/hcp/ccp.
High tensile strength.
Ex: Fe various forms.
Exceptions Zn soft.
10. Why Zn not transition?
4 Marks Answer:
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.
6 Marks Answer:
(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.
6 Marks Answer:
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.
6 Marks Answer:
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.
6 Marks Answer:
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.
6 Marks Answer:
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.
6 Marks Answer:
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.
6 Marks Answer:
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.
6 Marks Answer:
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?
6 Marks Answer:
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.
6 Marks Answer:
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.
3 Marks Answer:
Groups 3-12, d filling.
Four series 3d-6d.
Incomplete d atom/ions.
Transitional s/p.
2. f-block position.
3 Marks Answer:
Bottom panel separate.
Lanthanoids Ce-Lu 4f.
Actinoids Th-Lr 5f.
Inner transition.
3. Why exceptions configs?
3 Marks Answer:
Half/full d stable.
Small d/s gap.
Ex: Cr d^5 s^1.
Cu d^{10} s^1.
4. Melting points high why?
3 Marks Answer:
d + s e- bonding.
Unpaired max mid.
4d/5d higher.
Ex: W high.
5. Atomic radii trend.
3 Marks Answer:
Decrease left-right.
Poor d shield.
3d <4d, 5d~4d.
Contraction effect.
6. Ionisation enthalpies irregular.
3 Marks Answer:
Increase general.
Breaks d^5 d^{10}.
2nd/3rd high.
Ex: Cr high 2nd.
7. Oxidation states variable.
3 Marks Answer:
d e- loss.
+2 common.
Max +7 Mn.
Stable half/full.
8. Lanthanoid contraction cause.
3 Marks Answer:
Poor 4f shielding.
Size decrease.
Nuclear charge increase.
5d~4d effect.
9. Why high atomisation enthalpies?
3 Marks Answer:
Unpaired e- bonds.
Max mid series.
Heavy stronger.
Noble metals.
10. Metallic structures types.
3 Marks Answer:
bcc, hcp, ccp.
Ex: Sc hcp/bcc.
Fe multiple.
Normal temp.
6 Marks Questions (10 Qs)
1. Distinguish d/f block.
6 Marks Answer:
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.
6 Marks Answer:
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.
6 Marks Answer:
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.
6 Marks Answer:
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.
6 Marks Answer:
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.
6 Marks Answer:
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.
6 Marks Answer:
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.
6 Marks Answer:
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.
6 Marks Answer:
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.
6 Marks Answer:
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).
