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Question: Answered & Verified by Expert
If the radius of the hydrogen atom is $53 \mathrm{pm}$, the radius of the $\mathrm{He}^{+}$ion is closest to
ChemistryStructure of AtomKVPYKVPY 2014 (SA)
Options:
  • A $108 \mathrm{pm}$
  • B $81 \mathrm{pm}$
  • C $27 \mathrm{pm}$
  • D $13 \mathrm{pm}$
Solution:
2463 Upvotes Verified Answer
The correct answer is: $27 \mathrm{pm}$
$r_{n}=\frac{R_{H} n^{2}}{Z}$
$r_{H_{e+}}=\frac{53 n^{2}}{Z}$ $=\frac{53 \times 1^{2}}{2}=27$ approx.

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