Answer: attains the stable 4f0 (noble gas) configuration.
- A is strongly hydrated
- B is a strong reducing agent
- C has a stable exactly half-filled 4f subshell
- D attains the stable 4f0 (noble gas) configuration
Correct answer: D. attains the stable 4f0 (noble gas) configuration
Explanation: Removing four electrons from Ce ([Xe]4f15d16s2) gives Ce4+ with an empty 4f (4f0) noble-gas-like configuration, which is unusually stable.
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.