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Atomic Radius

Easychemistry

Across period 3 from Na to Cl, the atomic radius generally decreases because:

Select the correct option:

Effective nuclear charge increases while electrons are added to the same shell

Shielding effect increases drastically due to addition of new inner shells

Nuclear charge remains constant but electron-electron repulsion rises

Number of occupied shells increases from left to right

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About This Question

Subject: chemistry
Chapter: classification of elements and periodicity in properties
Topic: atomic radius
Difficulty: Easy
Year: 2025

Solution

Correct Answer:

Effective nuclear charge increases while electrons are added to the same shell

From Na to Cl, protons are added to the nucleus while electrons enter the same principal shell (n = 3). Shielding does not increase enough to cancel this rise in nuclear attraction. Therefore effective nuclear charge increases and pulls electrons closer, reducing atomic radius.

This easy difficulty chemistry question is from the chapter classification of elements and periodicity in properties, covering the topic of atomic radius. It appeared in the 2025 exam.

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