The d- and f-block elements are known as transition elements and inner transition elements, respectively. These elements play a crucial role in industrial chemistry, catalysis, metallurgy, and biological systems.
👉 Core Idea: These elements have partially filled d or f orbitals, which give them unique properties like variable oxidation states, color, and magnetic behavior.
1. Position in Periodic Table
d-Block Elements
- Located in the middle of the periodic table
- Groups 3 to 12
- Transition metals
f-Block Elements
- Located at the bottom (lanthanides & actinides)
- Inner transition elements
Diagram (Position)
s-block | d-block | p-block
|
f-block (below)
2. Electronic Configuration
d-Block
General configuration:
(n−1)d¹–¹⁰ ns⁰–²
Example
Fe → [Ar] 3d⁶ 4s²
f-Block
General configuration:
(n−2)f¹–¹⁴ (n−1)d⁰–¹ ns²
Example
Ce → [Xe] 4f¹ 5d¹ 6s²
Concept Clarity
👉 WHY irregular configurations occur?
Because half-filled and fully filled orbitals are more stable.
3. General Properties of d-Block Elements
(A) Metallic Nature
- Hard and dense
- High melting points
(B) Variable Oxidation States
Example:
- Fe → +2, +3
- Mn → +2 to +7
Concept Clarity
👉 WHY variable oxidation states?
Because both ns and (n−1)d electrons participate.
(C) Formation of Coloured Compounds
Transition metals form coloured ions.
Reason
Due to d–d electronic transitions
Diagram (d-Orbital Splitting)
Higher energy: eg
Lower energy: t2g
(D) Magnetic Properties
Types
- Paramagnetic → unpaired electrons
- Diamagnetic → no unpaired electrons
Formula
μ = √n(n+2)
4. Catalytic Properties
Transition metals act as catalysts.
Examples
- Fe → Haber process
- V₂O₅ → Contact process
Concept Clarity
👉 WHY catalysts?
Because they can change oxidation states easily.
5. Formation of Complex Compounds
Transition metals form coordination compounds.
Example
[Fe(CN)₆]³⁻
Reason
- Small size
- High charge
- Availability of d-orbitals
6. Interstitial Compounds
Definition
Small atoms (H, C, N) occupy spaces in metal lattice.
Properties
- Hard
- High melting point
7. Alloys
Mixtures of metals.
Examples
- Steel (Fe + C)
- Brass (Cu + Zn)
8. f-Block Elements
Types
(A) Lanthanides (4f series)
- Atomic number: 57–71
(B) Actinides (5f series)
- Atomic number: 89–103
9. Lanthanides
General Configuration
[Xe] 4f¹–¹⁴ 5d⁰–¹ 6s²
Properties
- Soft metals
- Highly reactive
- Mostly +3 oxidation state
Lanthanide Contraction (Very Important)
Definition
Gradual decrease in atomic size across lanthanides.
Reason
Poor shielding of 4f electrons
Diagram
La → Ce → Nd → ... → Lu
(Size decreases gradually)
Effects
- Similar properties
- Difficulty in separation
10. Actinides
General Configuration
[Xe] 5f¹–¹⁴ 6d⁰–¹ 7s²
Properties
- Radioactive
- Variable oxidation states
Common Oxidation States
+3, +4, +5, +6
Concept Clarity
👉 WHY actinides show more oxidation states?
Because 5f, 6d, and 7s electrons participate.
11. Comparison: Lanthanides vs Actinides
| Lanthanides | Actinides |
|---|---|
| Less reactive | More reactive |
| Mostly +3 state | Variable states |
| Non-radioactive | Radioactive |
12. Important Trends
Atomic Size
Decreases across series
Ionization Energy
Increases gradually
Reactivity
High due to metallic nature
13. Important Compounds
- KMnO₄ (oxidizing agent)
- K₂Cr₂O₇ (oxidizing agent)
14. Applications
- Catalysts
- Alloys
- Magnets
- Nuclear fuels (Uranium)
15. Important Reactions
Oxidation reactions
MnO₄⁻ → Mn²⁺
Reduction reactions
Cr₂O₇²⁻ → Cr³⁺
16. Concept Clarity Section (Very Important)
👉 WHY d-block elements are coloured?
Due to d–d transitions.
👉 WHY lanthanides show contraction?
Because 4f electrons shield poorly.
👉 WHY actinides are radioactive?
Because of unstable nuclei.
👉 WHY transition metals form complexes?
Due to availability of vacant d-orbitals.
17. Common Mistakes
- Confusing d and f block
- Ignoring oxidation states
- Wrong electronic configuration
Conclusion
d- and f-block elements are crucial for understanding advanced inorganic chemistry. Their unique properties make them highly useful in industrial and biological applications.
👉 Focus on:
- Electronic configuration
- Oxidation states
- Lanthanide contraction
- Colour and magnetism