Answer: Progressive decrease in atomic/ionic radii from La to Lu due to poor shielding by 4f electrons.
- A Progressive decrease in atomic/ionic radii from La to Lu due to poor shielding by 4f electrons
- B A steady increase in both atomic and ionic radii moving from La all the way to Lu
- C The spontaneous radioactive decay process observed uniformly across the whole lanthanide series
- D The gradual stepwise loss of all fourteen 4f electrons moving from La through to Lu
Correct answer: A. Progressive decrease in atomic/ionic radii from La to Lu due to poor shielding by 4f electrons
Explanation: As 4f electrons are added across the lanthanide series, poor shielding by 4f orbitals allows increasing nuclear charge to contract the atom/ion progressively.
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.