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How does a Na⁺ ion compare in size to a neutral Na atom?
ASmaller because of lost outer shell
BSame size
CLarger because of gained electrons
DTwice as large
Answer & Solution
Correct answer: A. Smaller because of lost outer shell
1. A sodium atom has the configuration 2, 8, 1.
2. The Na⁺ ion forms by losing the single 3s electron.
3. After losing this electron the outermost shell becomes the second shell.
4. So the principal quantum number of the outer shell drops by one.
5. The ion also experiences less electron-electron repulsion.
6. Hence Na⁺ is smaller than the parent Na atom.
_Source: Selina Concise Chemistry ICSE Class 10, Ch 1 'Periodic Table' (aplustopper.com extract)_
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