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

Elements of the 6th and 7th period in Groups 4-10 have nearly identical atomic radii to their 5th period counterparts. This is called:

Answer: Lanthanide contraction.

A Lanthanide contraction
B Actinide expansion
C Diagonal relationship
D Inert pair effect

Correct answer: A. Lanthanide contraction

Explanation: Lanthanide contraction: filling of 4f orbitals (poor shielding) causes a gradual size decrease, making 5d elements nearly the same size as their 4d analogues.

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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Elements of the 6th and 7th period in Groups 4-10 have nearly identical atomic radii to their 5th period counterparts. This is called:

Concept context

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