Chapter 4: The d- and f- Block Elements - Comprehensive NEET Chemistry Notes

1. The d-Block Elements

1.1 Introduction to the d-Block Elements

The d-block of the periodic table includes elements from groups 3 to 12, where the d orbitals are progressively filled. These elements are also known as transition metals. The series of transition metals are:

3d series: Sc to Zn
4d series: Y to Cd
5d series: La and Hf to Hg
6d series: Ac and elements from Rf to Cn

1.2 Electronic Configuration

The general electronic configuration for d-block elements is $(n - 1) d^{1 - 10} n s^{1 - 2}$ . Exceptions occur due to the stability of half-filled and fully filled d-orbitals, such as Cr ( $3 d^{5} 4 s^{1}$ ) and Cu ( $3 d^{5} 4 s^{1} 0$ ).

1.3 General Properties

Metallic Properties: High tensile strength, ductility, malleability, and high thermal and electrical conductivity.
Oxidation States: Exhibit variable oxidation states due to the participation of both nnn and n−1n-1n−1 electrons.
Catalytic Properties: Many transition metals act as catalysts due to their ability to adopt multiple oxidation states.
Formation of Colored Ions: Due to d-d electronic transitions.
Formation of Complex Compounds: High charge density and availability of d-orbitals facilitate complex formation.

2. The f-Block Elements

2.1 Introduction to the f-Block Elements

The f-block consists of lanthanoids (4f series) and actinoids (5f series). These elements are placed separately at the bottom of the periodic table. Lanthanoids and actinoids are also referred to as inner transition metals.

2.2 Electronic Configuration

Lanthanoids have the general electronic configuration $[X e] 4 f^{1 - 14} 5 d^{0 - 1} 6 s^{2}$ , while actinoids have $[R n] 5 f^{1 - 14} 6 d^{0 - 1} 7 s^{2}$ .

2.3 General Properties

Lanthanoid Contraction: A regular decrease in atomic and ionic sizes from La to Lu.
Oxidation States: Common oxidation state is +3, but +2 and +4 states also occur in some elements.
Color and Magnetic Properties: Many lanthanoids and actinoids are colored and paramagnetic due to unpaired f-electrons.
Chemical Reactivity: Actinoids are highly reactive, especially with non-metals.

3. Important Compounds of d-Block Elements

3.1 Potassium Dichromate ( $K_{2} C r_{2} O_{7}$ )

Preparation: Made from sodium chromate ( $N a_{2} C r O_{4}$ ) by acidifying with $H_{2} S O_{4} H_{2} S O_{4}$ .
Properties: Orange crystals, strong oxidizing agent.
Uses: Oxidizing agent in organic chemistry and volumetric analysis.

3.2 Potassium Permanganate ( $K M n O_{4}$ )

Preparation: Made by fusion of $M n O_{2}$ with KOH and oxidizing agents.
Properties: Dark purple crystals, strong oxidizing agent.
Uses: Oxidizing agent in organic chemistry, analytical chemistry, and bleaching textiles.

Quick Recap

d-block elements: Transition metals with variable oxidation states and complex formation.
f-block elements: Inner transition metals with lanthanoid contraction and high reactivity.
Potassium dichromate and permanganate: Important compounds with strong oxidizing properties.

Practice Questions

Explain why transition elements exhibit variable oxidation states.
Describe the lanthanoid contraction and its consequences.
Calculate the magnetic moment of $F e^{3 +}$ with $d^{5}$ configuration.
What are the uses of potassium dichromate in volumetric analysis?
Explain the preparation of potassium permanganate.

This chapter aims to ensure comprehensive understanding and high-scoring potential for NEET aspirants by covering critical aspects of d- and f-block elements, their properties, and important compounds.