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Why does atomic radius decrease while moving from left to right within a period?
AIncreasing nuclear charge pulls the same-shell electrons inward
BA brand-new outer electron shell is added each step
CThe number of neutrons falls sharply
DElectrons get removed from the outermost shell
Answer & Solution
Correct answer: A. Increasing nuclear charge pulls the same-shell electrons inward
1. Across a period the atomic number rises one unit at a time.
2. The extra electron enters the same outermost shell.
3. The higher nuclear charge pulls those electrons closer, shrinking the atom.
4. Rule out B: a new shell is added down a group, not across a period.
5. Rule out D: no electrons are removed when crossing a period.
_Source: Balbharati (Maharashtra Board) Class 10 Science & Technology, Ch 2 "Periodic Classification of Elements", p.34_
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