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A hydrogen atom and a Li^(2+) ion are b...

A hydrogen atom and a `Li^(2+)` ion are both in the second excited state. If `l_H` and `l_(Li)` are their respective electronic angular momenta, and `E_H and E_(Li)` their respective energies, then

A

`l_(H)gtl_(Li) and |E_(H)|gt|E_(Li)|`

B

`l_(H)=l_(Li) and |E_(H)|lt|E_(Li)|`

C

`l_(H)ltl_(Li) and |E_(H)|gt|E_(Li)|`

D

`l_(H)gtl_(Li) and |E_(H)|gtgt|E_(Li)|`

Text Solution

AI Generated Solution

The correct Answer is:
To solve the problem, we need to analyze the angular momentum and energy of a hydrogen atom and a lithium ion in the second excited state. ### Step-by-Step Solution: 1. **Identify the Quantum Numbers**: - The second excited state corresponds to the principal quantum number \( n = 3 \) for both the hydrogen atom (H) and the lithium ion (\( Li^{2+} \)). 2. **Calculate Angular Momentum**: - The angular momentum \( L \) of an electron in a hydrogen-like atom is given by the formula: \[ L = n \frac{h}{2\pi} \] - Since both atoms are in the same state (\( n = 3 \)), the angular momentum for both will be: \[ L_H = L_{Li} = 3 \frac{h}{2\pi} \] - Therefore, we conclude that: \[ l_H = l_{Li} \] 3. **Calculate Energy**: - The energy of an electron in a hydrogen-like atom is given by: \[ E = -\frac{13.6 Z^2}{n^2} \text{ eV} \] - For hydrogen (\( Z = 1 \)): \[ E_H = -\frac{13.6 \times 1^2}{3^2} = -\frac{13.6}{9} \text{ eV} \] - For lithium (\( Z = 3 \)): \[ E_{Li} = -\frac{13.6 \times 3^2}{3^2} = -\frac{13.6 \times 9}{9} = -13.6 \text{ eV} \] - The magnitudes of the energies are: \[ |E_H| = \frac{13.6}{9} \text{ eV} \quad \text{and} \quad |E_{Li}| = 13.6 \text{ eV} \] - Since \( |E_{Li}| > |E_H| \), we conclude that: \[ |E_{Li}| > |E_H| \] 4. **Final Relations**: - From the above calculations, we have: \[ l_H = l_{Li} \quad \text{and} \quad |E_{Li}| > |E_H| \] ### Conclusion: The correct relation is: - Angular momentum of hydrogen and lithium are equal: \( l_H = l_{Li} \) - The energy of lithium is greater in magnitude than that of hydrogen: \( |E_{Li}| > |E_H| \)
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