JEE Main 2025 Jan 22 Shift 1, Chemistry Q9: Bohr's Atomic Model

JEE Main2025Jan 22, Shift 1Chemistry

Radius of the first excited state of Helium ion is given as :

$a_{0} \to$ radius of first stationary state of hydrogen atom.

Solution

Bohr radius formula: $r_{n} = a_{0} \frac{n ^{2}}{Z}$ .

For He $^{+}$ (a hydrogen-like ion), $Z = 2$ , and the first excited state is $n = 2$ .

$r = a_{0} \cdot \frac{2 ^{2}}{2} = 2 a_{0}$ .

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