Question:
What is the radius of first orbit of monopositive helium ion?
What is the radius of first orbit of monopositive helium ion?
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Formula: \(r \propto \frac{1}{Z}\) → higher Z, smaller radius.
Updated On: May 4, 2026
- 13.23 pm
- 26.45 pm
- 39.68 pm
- 19.84 pm
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The Correct Option is B
Solution and Explanation
Concept:
Bohr radius formula: \[ r_n = \frac{0.529 \times n^2}{Z} \text{ Å} \]
Step 1: For He$^+$
• \(Z = 2\)
• \(n = 1\)
Step 2: Calculate radius. \[ r = \frac{0.529}{2} = 0.2645 \text{ Å} \]
Step 3: Convert to pm. \[ 1 \text{ Å} = 100 \text{ pm} \] \[ r = 0.2645 \times 100 = 26.45 \text{ pm} \] Conclusion: \[ \text{Radius = 26.45 pm} \]
Bohr radius formula: \[ r_n = \frac{0.529 \times n^2}{Z} \text{ Å} \]
Step 1: For He$^+$
• \(Z = 2\)
• \(n = 1\)
Step 2: Calculate radius. \[ r = \frac{0.529}{2} = 0.2645 \text{ Å} \]
Step 3: Convert to pm. \[ 1 \text{ Å} = 100 \text{ pm} \] \[ r = 0.2645 \times 100 = 26.45 \text{ pm} \] Conclusion: \[ \text{Radius = 26.45 pm} \]
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