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NEET CHEMISTRYThe d-and f-Block ElementsMedium

Question

Which of the following pairs has the same size?

A

Fe²⁺, Ni²⁺

B

Zr⁴⁺, Ti⁴⁺

C

Zr⁴⁺, Hf⁴⁺

D

Zn²⁺, Hf⁴⁺

Step-by-Step Solution

Usually, atomic and ionic radii increase down a group due to the addition of a new electron shell. However, the radii of the second (4d) and third (5d) transition series are virtually the same (e.g., Zr ≈ 160 pm, Hf ≈ 159 pm). This is due to Lanthanoid Contraction.

The filling of 4f orbitals before the 5d series results in poor shielding of the nuclear charge by the 4f electrons. This causes a greater effective nuclear charge to pull the outer electrons closer, shrinking the size of 5d elements (like Hf) to be almost identical to their 4d counterparts (like Zr). Consequently, Zr4+Zr^{4+} and Hf4+Hf^{4+} have almost the same ionic radii.

Exam Context & Concepts Covered

This question aligns with the NEET CHEMISTRY syllabus, specifically targeting concepts from The d-and f-Block Elements. Mastering this topic is crucial for scoring well in the upcoming medical entrance examinations. Solving conceptually related problems will help you understand the nuances of these concepts and improve your problem-solving speed.

CHEMISTRYThe d-and f-Block Elementsfollowing

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