CBSE Class 12 Chemistry – The d- and f-Block Elements

Chapter Overview

This chapter discusses the d-block (transition elements) and f-block (inner transition elements) of the periodic table. It covers their electronic configurations, physical and chemical properties, oxidation states, complex formation, catalytic behavior, and color. The f-block elements—lanthanides and actinides—are also introduced with emphasis on lanthanide contraction and their chemical characteristics.

Important Keywords

• Transition Elements: Elements of groups 3 to 12 in the periodic table with partially filled d-orbitals.
• Inner Transition Elements: Elements with partially filled f-orbitals (lanthanides and actinides).
• Lanthanides: 14 elements from cerium (Ce) to lutetium (Lu).
• Actinides: 14 elements from thorium (Th) to lawrencium (Lr).
• Lanthanide Contraction: Gradual decrease in ionic radii across the lanthanide series.
• Variable Oxidation States: Ability of d-block elements to exhibit more than one oxidation state.
• Catalytic Property: Property of transition metals to act as catalysts due to variable oxidation states and surface area.
• Complex Compounds: Compounds with a central metal atom/ion bonded to ligands.
• Color of Compounds: Due to d–d electronic transitions.
• Paramagnetism: Property due to unpaired electrons in d or f orbitals.