d and f Block Elements

part 1

Position and Electronic Configuration

• Position in periodic table
• Electronic configuration of d-block elements
• General properties — atomic radii, ionisation enthalpy

part 2

Properties of Transition Elements

• Variable oxidation states
• Magnetic properties
• Formation of coloured compounds
• Catalytic properties
• Formation of complex compounds
• Interstitial compounds and alloy formation

part 3

Important Compounds and f-Block

• Important compounds of chromium and manganese
• KMnO₄ and K₂Cr₂O₇ — preparation and uses
• Lanthanoids — electronic configuration and properties
• Actinoids — electronic configuration and properties

Magnetic moment formula

$\mu = \sqrt{n(n+2)}$ BM (n = unpaired electrons)

★ board favourite

Electronic config of transition metals (general)

$(n-1)d^{1-10}\, ns^{1-2}$

★ frequently asked

Oxidation states: variable due to d-electrons

e.g. Mn: +2,+3,+4,+6,+7

★ frequently asked

KMnO₄: structure and oxidising action

MnO₄⁻ → Mn²⁺ (acidic); MnO₄⁻ → MnO₂ (neutral/basic)

★ frequently asked

K₂Cr₂O₇: dichromate structure and reactions

Cr₂O₇²⁻ + 14H⁺ + 6e⁻ → 2Cr³⁺ + 7H₂O

★ frequently asked

Describe the preparation of potassium permanganate from pyrolusite ore. Write the ionic equations for its reaction with (i) oxalic acid and (ii) ferrous sulphate in acidic medium.

Calculate the spin-only magnetic moment of the Fe²⁺ ion. (Atomic number of Fe = 26)

Why is Zn²⁺ colourless whereas Cu²⁺ is coloured in aqueous solution?

Explain the following: (i) The E°(M²⁺/M) value for copper is positive (+0.34 V). (ii) The Eº(Mn³⁺/Mn²⁺) is much more positive than that of Cr³⁺/Cr²⁺. (iii) The highest oxidation state is exhibited in oxides and fluorides.

What is lanthanoid contraction? State any two of its consequences.

(a) Describe the preparation of potassium dichromate from chromite ore. (b) What happens when the pH of a dichromate solution is increased? Write the equation. (c) Draw the structures of the chromate and dichromate ions.

Account for the following: (i) Transition metals show variable oxidation states. (ii) Zn, Cd and Hg are not regarded as transition elements. (iii) Transition metals form a large number of coloured compounds.

Why do the lanthanoids show a limited number of oxidation states, mainly +3?

Explain: (i) Transition metals have high enthalpies of atomisation. (ii) The atomic radii of the 4d and 5d series elements in the same group are nearly the same. (iii) Mn²⁺ compounds are more stable than Fe²⁺ towards oxidation to +3 state.

Write two differences between the chemistry of lanthanoids and that of actinoids.

What are interstitial compounds? Why are they well known for transition metals?

How many marks is d and f Block Elements worth in the Class 12 board exam?

Around 7 marks of the 70-mark CBSE Chemistry theory paper, based on the official unit-wise weightage. Properties of transition metals + KMnO₄ & K₂Cr₂O₇ reactions.

Is d and f Block Elements easy or hard?

It's rated medium — a moderate-difficulty chapter in Class 12 Chemistry. Most students need about 3 hours to cover it well.

What are the important topics in d and f Block Elements?

The chapter covers 12 NCERT topics in 3 areas: Position and Electronic Configuration; Properties of Transition Elements; Important Compounds and f-Block.

What questions come from d and f Block Elements in board exams?

Between 2018–2024, CBSE board papers asked questions from this chapter on Preparation of KMnO₄, Magnetic Properties, Colour of Ions, Trends in Transition Series — 1- to 5-mark questions.