NEET2025Chemistry-Atomic Structure

NEET 2025 Chemistry Bohr Model MCQ Question

Type: MCQ-numerical-Medium-Class 11

Energy and radius of first Bohr orbit of He⁺ and Li²⁺ are

[Given Rₕ = 2.18 × 10⁻¹⁸ J, a₀ = 52.9 pm]

A

Eₙ(Li²⁺) = -19.62×10⁻¹⁸ J; rₙ(Li²⁺) = 17.6 pm Eₙ(He⁺) = -8.72×10⁻¹⁸ J; rₙ(He⁺) = 26.4 pm

B

Eₙ(Li²⁺) = -8.72×10⁻¹⁸ J; rₙ(Li²⁺) = 26.4 pm Eₙ(He⁺) = -19.62×10⁻¹⁸ J; rₙ(He⁺) = 17.6 pm

C

Eₙ(Li²⁺) = -8.72×10⁻¹⁶ J; rₙ(Li²⁺) = 17.6 pm Eₙ(He⁺) = -19.62×10⁻¹⁶ J; rₙ(He⁺) = 26.4 pm

D

Eₙ(Li²⁺) = -8.72×10⁻¹⁶ J; rₙ(Li²⁺) = 17.6 pm Eₙ(He⁺) = -19.62×10⁻¹⁶ J; rₙ(He⁺) = 17.6 pm

Correct Answer

Option A

Detailed Explanation

Using the Bohr model, the energy and radius for the first orbit can be calculated using the formulas Eₙ = -RₕZ²/n² and rₙ = a₀n²/Z. For Li²⁺ (Z=3) and He⁺ (Z=2), the calculations match option 1.

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