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If the radius of the second Bohr's orbit of a hydrogen atom is a₀, then the radius of the third Bohr's orbit of a Be³⁺ ion will be:

Correct answer: A. 9/16. a₀

  • A. 9/16. a₀
  • B. 3a₀
  • C. 1.5a₀
  • D. 4a₀

Explanation

The Bohr radius is given by r ∝ n²/Z. The radius of the second orbit of H (n=2, Z=1 is proportional to 4). The radius of the third orbit of Be³⁺ (n=3, Z=4 is proportional to 9/4). The ratio is (9/4)/4 = 9/16 of the H (n=1 radius). So, the radius of the 3rd Bohr orbit of Be= 9/16 a₀.

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