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← JEE Main 2026 · 2 Apr · Shift 2
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JEE Main 2026 · 2 Apr · Shift 2, Physics question 44

The binding energy per nucleon of 83209Bi{}^{209}_{83}Bi is ________ MeV.
[Take m(83209Bi)=208.980388m\left({}^{209}_{83}Bi\right)=208.980388 u, mp=1.007825m_p=1.007825 u, mn=1.008665m_n=1.008665 u, 1 u = 931 MeV/c²]

Choose one option
Answer and worked solution

Official answer: B

Mass defect.
Δm=83(1.007825)+126(1.008665)−208.980388=1.760877 u.\Delta m=83(1.007825)+126(1.008665)-208.980388=1.760877\text{ u}.

Binding energy. 1.760877×931=1639.41.760877\times931=1639.4 MeV; per nucleon 1639.4209=7.84\frac{1639.4}{209}=7.84 MeV.

(B)