JEE · Chemistry

d- and f-Block Elements

Explain transition and inner-transition behaviour from d or f electron configuration, oxidation-state stability, size, colour, magnetism, catalysis, alloying and verified redox chemistry.

Subject: Chemistry
Syllabus unit: The d- and f-Block Elements
Updated: 8 September 2026

Mapped to JEE Main 2026 and JEE Advanced 2026
Configuration-to-property reasoning, not memorised exceptions
No invented weightage, question counts or trend percentages

Content status: draft. Verified academic content for this page has not been loaded yet, so the page is excluded from search indexing and the sitemap.

In short

d- and f-block behaviour is not a list of unrelated exceptions. Begin with the atom or ion's electron configuration, identify accessible oxidation states and unpaired electrons, then connect size, field environment, redox potential and structure to colour, magnetism, catalysis, alloying or compound behaviour.

Syllabus mapping

Syllabus mapping
Unit	Topics
The d- and f-Block Elements	Transition-element configuration and occurrence, First-row physical trends, ionization enthalpy, oxidation states, radii, Colour, catalysis, magnetism and complex formation, Interstitial compounds and alloys, Preparation, properties and uses of K2Cr2O7 and KMnO4, Lanthanoid configuration, oxidation states and contraction, Actinoid configuration and oxidation states, d-block oxidation-state stability and standard electrode potentials (Advanced), Chromium and manganese oxoanion preparation, structure and reactions (Advanced)

Unit
The d- and f-Block Elements
Topics
Transition-element configuration and occurrence, First-row physical trends, ionization enthalpy, oxidation states, radii, Colour, catalysis, magnetism and complex formation, Interstitial compounds and alloys, Preparation, properties and uses of K2Cr2O7 and KMnO4, Lanthanoid configuration, oxidation states and contraction, Actinoid configuration and oxidation states, d-block oxidation-state stability and standard electrode potentials (Advanced), Chromium and manganese oxoanion preparation, structure and reactions (Advanced)

What this chapter contains and why it matters

What this chapter contains and why it matters
Question	Direct answer
What is the chapter about?	How d- and f-block elemental and ionic behaviour follows from electron configuration: oxidation states, size, colour, magnetism, catalysis, alloying, interstitial compounds, and specified chromium and manganese chemistry.
What is the central method choice?	Start from the atom or ion's configuration, then test the consequence for oxidation state, size, colour, magnetism or reactivity, checking the medium for redox reactions.
Where do most mistakes begin?	Removing electrons in the wrong order, treating configuration ranges as exception-free, predicting colour from d electrons alone, and applying an acidic permanganate or dichromate equation in basic medium.
What should come before this chapter?	Atomic Structure, Periodic Table trends, and Redox Reactions half-reaction balancing.
What comes after it?	Coordination Compounds develops ligand-field structure and complex properties; this chapter keeps that depth on its own route.

Question
What is the chapter about?
Direct answer
How d- and f-block elemental and ionic behaviour follows from electron configuration: oxidation states, size, colour, magnetism, catalysis, alloying, interstitial compounds, and specified chromium and manganese chemistry.
Question
What is the central method choice?
Direct answer
Start from the atom or ion's configuration, then test the consequence for oxidation state, size, colour, magnetism or reactivity, checking the medium for redox reactions.
Question
Where do most mistakes begin?
Direct answer
Removing electrons in the wrong order, treating configuration ranges as exception-free, predicting colour from d electrons alone, and applying an acidic permanganate or dichromate equation in basic medium.
Question
What should come before this chapter?
Direct answer
Atomic Structure, Periodic Table trends, and Redox Reactions half-reaction balancing.
Question
What comes after it?
Direct answer
Coordination Compounds develops ligand-field structure and complex properties; this chapter keeps that depth on its own route.

The official JEE documents define content scope. They do not publish chapter weightage, so none is asserted here.

Official JEE syllabus mapping for d- and f-Block Elements

Verified against the current JEE Main 2026 syllabus and JEE Advanced 2026 syllabus on 8 September 2026. This is a wording and scope mapping, not a claim about question difficulty or frequency.

Official JEE syllabus mapping for d- and f-Block Elements
Concept group	JEE Main 2026	JEE Advanced 2026	Preparation note
Transition-element configuration, occurrence, physical trends	Explicitly listed: configuration, occurrence, first-row physical trends, ionization enthalpy, oxidation states, radii.	Not restated as a separate physical-trend list; oxidation-state stability and standard electrode potentials are named directly.	Build the configuration-to-trend chain before memorising any single trend line.
Colour, magnetism, catalysis, complex formation	Explicitly listed alongside interstitial compounds and alloys.	Catalysis and applications are explicitly listed.	State the species and environment before asserting colour or magnetism.
Chromium and manganese oxoanion chemistry	Preparation, properties and uses of K2Cr2O7 and KMnO4 are explicitly listed.	Preparation, structure and reactions of chromium and manganese oxoanions are explicitly listed.	Keep permanganate and dichromate half-reactions medium-specific.
Lanthanoid and actinoid chemistry	Lanthanoid configuration, oxidation states and contraction; actinoid configuration and oxidation states are explicitly listed.	Lanthanoid and actinoid contractions, oxidation states and general characteristics are explicitly listed.	Compare contraction claims within the same series using a like-for-like radius definition.
Ligand-field structure and complex geometry	Not treated in depth on this route.	Not treated in depth on this route.	This depth is owned by the Coordination Compounds chapter.

Concept group
Transition-element configuration, occurrence, physical trends
JEE Main 2026
Explicitly listed: configuration, occurrence, first-row physical trends, ionization enthalpy, oxidation states, radii.
JEE Advanced 2026
Not restated as a separate physical-trend list; oxidation-state stability and standard electrode potentials are named directly.
Preparation note
Build the configuration-to-trend chain before memorising any single trend line.
Concept group
Colour, magnetism, catalysis, complex formation
JEE Main 2026
Explicitly listed alongside interstitial compounds and alloys.
JEE Advanced 2026
Catalysis and applications are explicitly listed.
Preparation note
State the species and environment before asserting colour or magnetism.
Concept group
Chromium and manganese oxoanion chemistry
JEE Main 2026
Preparation, properties and uses of K2Cr2O7 and KMnO4 are explicitly listed.
JEE Advanced 2026
Preparation, structure and reactions of chromium and manganese oxoanions are explicitly listed.
Preparation note
Keep permanganate and dichromate half-reactions medium-specific.
Concept group
Lanthanoid and actinoid chemistry
JEE Main 2026
Lanthanoid configuration, oxidation states and contraction; actinoid configuration and oxidation states are explicitly listed.
JEE Advanced 2026
Lanthanoid and actinoid contractions, oxidation states and general characteristics are explicitly listed.
Preparation note
Compare contraction claims within the same series using a like-for-like radius definition.
Concept group
Ligand-field structure and complex geometry
JEE Main 2026
Not treated in depth on this route.
JEE Advanced 2026
Not treated in depth on this route.
Preparation note
This depth is owned by the Coordination Compounds chapter.

Sources: JEE Main 2026 syllabus and JEE Advanced 2026 syllabus, both linked in the sources section below.

Before this chapter

Prerequisites: what you should know before this chapter

Prerequisites: what you should know before this chapter
Prerequisite	You are ready if you can…	If not, repair this first
Atom and ion configurations	Write ground-state configurations and predict which electrons leave first on cation formation.	Revise Aufbau order and configuration writing in Atomic Structure.
Oxidation-number rules	Assign oxidation states in a compound or ion without ambiguity.	Revise oxidation-number rules and worked examples.
Redox half-reaction balancing	Balance atoms, charge and electrons in that order for a half-reaction.	Revise half-reaction balancing in Redox Reactions.
Periodic size trends	Explain why shielding changes radius trends across a period.	Revise effective nuclear charge and shielding in Periodic Table.

Prerequisite
Atom and ion configurations
You are ready if you can…
Write ground-state configurations and predict which electrons leave first on cation formation.
If not, repair this first
Revise Aufbau order and configuration writing in Atomic Structure.
Prerequisite
Oxidation-number rules
You are ready if you can…
Assign oxidation states in a compound or ion without ambiguity.
If not, repair this first
Revise oxidation-number rules and worked examples.
Prerequisite
Redox half-reaction balancing
You are ready if you can…
Balance atoms, charge and electrons in that order for a half-reaction.
If not, repair this first
Revise half-reaction balancing in Redox Reactions.
Prerequisite
Periodic size trends
You are ready if you can…
Explain why shielding changes radius trends across a period.
If not, repair this first
Revise effective nuclear charge and shielding in Periodic Table.

This is a readiness check, not a weightage or scoring-priority list.

Concepts in this chapter

1. Write the configuration before assigning any property

Remove electrons from the outer ns shell before (n-1)d when forming common transition-metal cations.

The general d-block organizing form is (n-1)d^1-10 ns^0-2, and the general f-block organizing form is (n-2)f^1-14 (n-1)d^0-1 ns^2. Neither is an exact formula for every element; atom-specific configurations must be verified. When a common cation forms, electrons leave the outer ns shell before the (n-1)d shell.

2. Oxidation-state stability needs more than one electron-count slogan

Compare accessible configurations, lattice or hydration effects, ligand environment, and redox potential together.

No single electron-count rule predicts every stability order. A stability claim needs the species, its accessible configurations, lattice or hydration effects where relevant, the ligand environment, and the redox potential considered together.

3. Transition-series size changes gradually because of incomplete shielding

d electrons shield incompletely across a series, so radii change more gradually than a simple main-group trend might suggest.

Across a transition series, d electrons shield the nuclear charge incompletely, so atomic and ionic radii change more gradually than a simple main-group trend would suggest.

4. Colour and magnetism both need the specific species and environment

Unpaired electrons support paramagnetism; colour may involve d-state transitions or charge-transfer effects.

Unpaired electrons support paramagnetism. Colour may arise from d-state transitions or from charge-transfer effects. A visible colour claim needs the actual ion and its environment stated, not a generic reference to 'having d electrons'.

5. Name the actual catalytic mechanism before claiming a cause

Multiple oxidation states, adsorption, and intermediate formation can all contribute to catalytic behaviour, but the actual mechanism must be specified before claiming a cause for a given reaction.

6. Lanthanoid and actinoid contraction come from poor f-electron shielding

Poor shielding by f electrons increases effective nuclear attraction across a series.

Poor shielding by f electrons increases effective nuclear attraction across a lanthanoid or actinoid series, producing a contraction in size. A contraction claim needs a like-for-like comparison of species, oxidation state, series position and radius type.

7. Store the full evidence record, not just the conclusion

For any trend, colour, magnetism, catalysis, or compound claim, store the compound, oxidation state, medium, temperature, balanced equation, observation, and source together, rather than the conclusion alone.

Method selector: choose the model before calculating

Match the question signal to the correct first model before any algebra or equation writing.

Method selector: choose the model before calculating
Question signal	Best first model	Required check
Atom or ion configuration	Electron count with ionization order	Neutral atom versus cation
Oxidation-state stability	Redox and environmental comparison	Medium, ligands and standard-state context
Magnetic moment	Unpaired-electron count	Free ion or defined complex environment
Colour	Electronic configuration plus transition type	Species, oxidation state and ligand or solvent environment
Cr or Mn oxoanion reaction	Half-reaction balance	Acidic, neutral or basic medium
Lanthanoid contraction	f-electron shielding model	Compare within the same series and oxidation state where appropriate

Question signal
Atom or ion configuration
Best first model
Electron count with ionization order
Required check
Neutral atom versus cation
Question signal
Oxidation-state stability
Best first model
Redox and environmental comparison
Required check
Medium, ligands and standard-state context
Question signal
Magnetic moment
Best first model
Unpaired-electron count
Required check
Free ion or defined complex environment
Question signal
Colour
Best first model
Electronic configuration plus transition type
Required check
Species, oxidation state and ligand or solvent environment
Question signal
Cr or Mn oxoanion reaction
Best first model
Half-reaction balance
Required check
Acidic, neutral or basic medium
Question signal
Lanthanoid contraction
Best first model
f-electron shielding model
Required check
Compare within the same series and oxidation state where appropriate

Conditional relations and evidence records

Every relation below carries its conditions and common trap; none is a universal formula divorced from context.

Conditional relations and evidence records
Expression or record	Meaning	Units	Conditions	Common trap
General d-block form (n-1)d^1-10 ns^0-2	Organizing configuration range, not every ground-state formula	Not applicable	Check known atom-specific configurations	Forcing every atom into one Aufbau pattern
General f-block form (n-2)f^1-14 (n-1)d^0-1 ns^2	Organizing inner-transition range	Not applicable	Atom-specific configurations require verification	Treating the range as an exact formula for every element
mu_so = sqrt(n(n+2))	Spin-only magnetic moment for n unpaired electrons	Bohr magnetons	Spin-only approximation	Counting total d electrons rather than unpaired electrons
MnO4- + 8H+ + 5e- -> Mn2+ + 4H2O	Permanganate reduction half-reaction	Charge and mole relation	Acidic aqueous medium	Using the Mn2+ product in neutral or basic medium without support
MnO4- + 2H2O + 3e- -> MnO2 + 4OH-	Permanganate reduction to manganese dioxide	Charge and mole relation	Neutral or basic aqueous model where MnO2 is the stated product	Copying acidic coefficients into a basic-medium answer
Cr2O7^2- + 14H+ + 6e- -> 2Cr3+ + 7H2O	Dichromate reduction half-reaction	Charge and mole relation	Acidic aqueous medium	Losing the factor of two for chromium atoms
Contraction record	Species, oxidation state, series position, radius type, and source, compared like for like	pm when numerical	Like-for-like comparison	Comparing unrelated coordination numbers or radius definitions

Expression or record
General d-block form (n-1)d^1-10 ns^0-2
Meaning
Organizing configuration range, not every ground-state formula
Units
Not applicable
Conditions
Check known atom-specific configurations
Common trap
Forcing every atom into one Aufbau pattern
Expression or record
General f-block form (n-2)f^1-14 (n-1)d^0-1 ns^2
Meaning
Organizing inner-transition range
Units
Not applicable
Conditions
Atom-specific configurations require verification
Common trap
Treating the range as an exact formula for every element
Expression or record
mu_so = sqrt(n(n+2))
Meaning
Spin-only magnetic moment for n unpaired electrons
Units
Bohr magnetons
Conditions
Spin-only approximation
Common trap
Counting total d electrons rather than unpaired electrons
Expression or record
MnO4- + 8H+ + 5e- -> Mn2+ + 4H2O
Meaning
Permanganate reduction half-reaction
Units
Charge and mole relation
Conditions
Acidic aqueous medium
Common trap
Using the Mn2+ product in neutral or basic medium without support
Expression or record
MnO4- + 2H2O + 3e- -> MnO2 + 4OH-
Meaning
Permanganate reduction to manganese dioxide
Units
Charge and mole relation
Conditions
Neutral or basic aqueous model where MnO2 is the stated product
Common trap
Copying acidic coefficients into a basic-medium answer
Expression or record
Cr2O7^2- + 14H+ + 6e- -> 2Cr3+ + 7H2O
Meaning
Dichromate reduction half-reaction
Units
Charge and mole relation
Conditions
Acidic aqueous medium
Common trap
Losing the factor of two for chromium atoms
Expression or record
Contraction record
Meaning
Species, oxidation state, series position, radius type, and source, compared like for like
Units
pm when numerical
Conditions
Like-for-like comparison
Common trap
Comparing unrelated coordination numbers or radius definitions

Medium changes both the product and the balanced coefficients for permanganate and dichromate reactions; never transport an acidic half-reaction into a neutral or basic problem.

Worked examples

Derive the balanced half-reaction for reduction of MnO4- to Mn2+ in acidic medium.

Answer: MnO4- + 8H+ + 5e- -> Mn2+ + 4H2O. The product and coefficients are medium-dependent; do not transport this acidic half-reaction into a neutral or basic problem.

Manganese is +7 in MnO4- and +2 in Mn2+, so it gains five electrons.

Balance the four oxygen atoms with 4 H2O on the product side.

Balance the eight hydrogen atoms with 8 H+ on the reactant side.

Check the left-side charge: -1 + 8 - 5 = +2, matching Mn2+.

Common mistakes and what they actually indicate

Removing d electrons before outer s electrons when forming common transition-metal cations.
Knowledge gap
Why it happens
Common transition-metal cations form by removing outer ns electrons before (n-1)d electrons; reversing the order gives a wrong configuration.
How it is corrected
Write the neutral-atom configuration first, then remove ns electrons before (n-1)d electrons for the cation.
Treating the general block configuration as exception-free for every element.
Knowledge gap
Why it happens
The general d-block and f-block forms are organizing ranges, not exact formulas for every element; some atom-specific configurations vary.
How it is corrected
Verify atom-specific configurations rather than forcing every element into one Aufbau pattern.
Predicting colour only from the presence of d electrons, without specifying the species and environment.
Decision / selection error
Why it happens
Colour may involve d-state transitions or charge-transfer effects, and a visible colour claim needs the actual ion and environment.
How it is corrected
State the exact ion, oxidation state and environment before asserting a colour.
Using spin-only magnetism without identifying unpaired electrons and environment.
Execution error
Why it happens
The spin-only formula uses the number of unpaired electrons, not the total d-electron count.
How it is corrected
Identify the unpaired-electron count for the correct species and environment before applying mu_so = sqrt(n(n+2)).
Applying an acidic permanganate or dichromate equation in basic medium.
Decision / selection error
Why it happens
Medium changes the stable manganese- or chromium-containing product and therefore the balanced half-reaction coefficients.
How it is corrected
Check the stated medium and use the matching half-reaction rather than copying acidic coefficients.
Calling every transition metal a catalyst for the same reason.
Needs review
Why it happens
Multiple oxidation states, adsorption, and intermediate formation can each contribute, but the actual mechanism must be specified for a given reaction.
How it is corrected
Name the specific catalytic mechanism for the stated reaction before claiming a cause.
Explaining lanthanoid contraction without a like-for-like radius comparison.
Recall gap
Why it happens
A contraction claim needs a controlled comparison; comparing unrelated coordination numbers or radius definitions is not valid evidence.
How it is corrected
Compare species within the same series, oxidation state and radius definition before asserting a contraction trend.

FAQ