Answer: Ability to change oxidation states and provide active surface for adsorption.
- A Ability to change oxidation states and provide active surface for adsorption
- B Their generally high molecular or atomic mass compared to other metals
- C Their predominantly ionic character in the bulk metallic state
- D Their underlying noble gas electron configuration
Correct answer: A. Ability to change oxidation states and provide active surface for adsorption
Explanation: Transition metals catalyse reactions by: (1) adsorbing reactants on their surface (heterogeneous) or (2) changing oxidation state to shuttle electrons (homogeneous).
Aqueous solutions of transition metal ions show characteristic colours caused by electrons absorbing visible light to jump between split d-orbitals; the exact colour depends on the metal, its oxidation state, and surrounding ligands.
Concept context
Transition metals (d-block) and lanthanides/actinides (f-block). Known for coloured compounds, variable oxidation states, complex formation, and catalytic properties. Frequently tested in JEE and NEET.