Answer: 5d elements (Period 6) are nearly the same size as 4d elements (Period 5) in the same group.
- A 5d elements (Period 6) are nearly the same size as 4d elements (Period 5) in the same group
- B All fifteen lanthanide elements end up with completely identical chemical properties
- C The entire d-block of the periodic table physically contracts in size
- D The lanthanide elements become progressively larger across the series
Correct answer: A. 5d elements (Period 6) are nearly the same size as 4d elements (Period 5) in the same group
Explanation: Lanthanide contraction causes Period 6 transition metals (5d) to be nearly the same size as their Period 5 (4d) counterparts, affecting their chemistry significantly.
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.