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

Radius of First Excited State of Helium Ion | JEE Mains PYQ | Structure of Atom

Q. Radius of the first excited state of Helium ion is given as : a₀ → radius of first stationary state of hydrogen atom.

(A) r = a₀/4

(B) r = 2a₀

(D) r = a₀/2

Explanation

Step 1: Formula for radius (Bohr model)

For hydrogen-like species:
r_n = a₀ × n² / Z

Step 2: Identify values

Helium ion = He⁺ → Z = 2
First excited state → n = 2

Step 3: Substitute values

r = a₀ × (2)² / 2
r = 4a₀ / 2
r = 2a₀

Correct Answer = r = 2a₀ (Option B)

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