d- and f-Block Elements
Free NCERT-aligned study resource for the 2026–27 academic session.
CBSE weightage: 7 marks. This unit is part of the official 70-mark Chemistry theory course for 2026–27. citeturn0search11
1. What You Need to Learn
Position and electronic configuration; general properties of transition elements; important compounds; lanthanoids; actinoids; applications.
2. Core Concepts & Formulae
Transition elements commonly show variable oxidation states, coloured ions, magnetic behaviour, catalytic activity and complex formation. Lanthanoid contraction is the gradual decrease in atomic/ionic radii across the lanthanoid series due to poor shielding by 4f electrons.
3. Common Mistakes
Memorise trends with reasons rather than isolated facts. Be careful with exceptional electronic configurations and oxidation states. For colour and magnetism, connect the answer to d-electrons and unpaired electrons.
4. Exam-Focused Practice
- Explain variable oxidation states in transition elements.
- Compare lanthanoid and actinoid trends.
- Explain lanthanoid contraction and give two consequences.
- Write important oxidation states and uses of selected compounds.
5. Quick Revision Checklist
- Can you define the key terms without looking at the book?
- Can you explain the main trend/reaction/mechanism with a reason?
- Can you solve a numerical or predict a product independently?
- Can you answer an application or competency-based question?