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Atomic radius generally DECREASES across a period because:
ANumber of shells decreases
BNuclear charge increases while shell number stays the same
CAtomic mass decreases by common convention
DNumber of neutrons rises
Answer & Solution
Correct answer: B. Nuclear charge increases while shell number stays the same
1. Across a period each new element adds one proton.
2. The added electron enters the same outer shell.
3. Greater nuclear charge pulls the outer shell inward.
4. Atomic radius therefore shrinks left to right.
5. The shell number does not change within a period.
_Source: NCERT Class 10 Science Ch 5 'Periodic Classification of Elements'_
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