🧪 Chemistry · Classification of Elements and Periodicity in Properties · NEET & JEE

As a direct consequence of the lanthanide contraction, which pair of elements has almost identical atomic radii?

Answer: Zr and Hf.

A Zr and Hf
B Fe and Co
C Na and K
D Cu and Ag

Correct answer: A. Zr and Hf

Explanation: The lanthanide contraction nearly cancels the expected size increase from period 5 to 6, making Zr and Hf almost equal in size.

The complete modern periodic table showing all 118 elements with atomic number, symbol, and atomic mass, color-coded by element category

The complete modern periodic table (118 elements). Image: Cepheus et al., Public Domain, via Wikimedia Commons.

Concept context

The periodic table organises all 118 elements by atomic number and similar properties. Study periodic trends like atomic radius, ionization energy, and electronegativity, and learn how an element's position predicts its behaviour.

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As a direct consequence of the lanthanide contraction, which pair of elements has almost identical atomic radii?

Concept context

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