Question

Assertion: The Zr-Hf pair of elements has the same value of atomic radii though Zr and Hf are placed in different periods in the periodic table.

Reason: The lanthanoid contraction prevents the expected increase in atomic radii of Hf.

Options

• Both Assertion and Reason are true and Reason is the correct explanation for Assertion.

• Both Assertion and Reason are true but Reason is not the correct explanation for Assertion.

• Assertion is true and Reason is false.

• Both Assertion and Reason are false.

Answer 1

Both Assertion and Reason are true and Reason is the correct explanation for Assertion.

Explanation:

Zirconium (Zr) and Hafnium (Hf) possess approximately equal atomic radii, despite their placement in distinct eras of the periodic table. This phenomenon arises from the lanthanoid contraction, which inhibits the anticipated increase in atomic size for Hf. The existence of lanthanides between Zr and Hf results in an increased nuclear attraction in Hf, hence diminishing its atomic radius to approximately that of Zr.