Which of the following has similar spectrum as that of `Li^(+)` :-

Options

A. H
B. `Na^(10+)`
C. He
D. `He^(+)`

Answer

To determine which of the following elements has a similar spectrum to that of \( \text{Li}^+ \), we need to analyze the electronic configuration of \( \text{Li}^+ \) and compare it with the other options.

### Step-by-Step Solution:

1. **Identify the Electronic Configuration of Lithium (Li)**:
- Lithium has an atomic number of 3, so its electronic configuration is:
\[ \text{Li: } 1s^2 \, 2s^1 \]

2. **Determine the Configuration of \( \text{Li}^+ \)**:
- When lithium loses one electron to form \( \text{Li}^+ \), it loses the outermost electron (2s electron):
\[ \text{Li}^+: 1s^2 \]

3. **Identify the Options**:
- We need to compare \( \text{Li}^+ \) with the provided options. Let's analyze each option one by one.

4. **Option Analysis**:
- **Hydrogen (H)**:
- Electronic configuration: \( 1s^1 \)
- Not similar to \( \text{Li}^+ \) (which has \( 1s^2 \)).

- **Sodium Ion (\( \text{Na}^{10+} \))**:
- Sodium has an atomic number of 11, so its configuration is:
\[ \text{Na: } 1s^2 \, 2s^2 \, 2p^6 \, 3s^1 \]
- Removing 10 electrons from sodium would leave:
\[ \text{Na}^{10+}: 1s^1 \]
- Not similar to \( \text{Li}^+ \).

- **Helium (He)**:
- Electronic configuration: \( 1s^2 \)
- This is identical to the configuration of \( \text{Li}^+ \).

- **Helium Ion (\( \text{He}^+ \))**:
- Removing one electron from helium gives:
\[ \text{He}^+: 1s^1 \]
- Not similar to \( \text{Li}^+ \).

5. **Conclusion**:
- The only element that has the same electronic configuration as \( \text{Li}^+ \) is Helium (\( \text{He} \)).
- Therefore, the answer is:
\[ \text{He} \]