Bohr theory is not applicable for

Options

A. `He^(+)`
B. `Li^(2+)`
C. `Br^(+)`
D. `H`

Answer

To determine where the Bohr theory is not applicable, we need to understand the conditions under which the Bohr model can be used. The Bohr model is primarily applicable to hydrogen and hydrogen-like species, which are defined as atoms or ions that have only one electron.

### Step-by-Step Solution:

1. **Understanding Bohr's Theory**:
- Bohr's theory is a model for the hydrogen atom that describes how electrons orbit the nucleus in quantized energy levels. It works well for hydrogen (H) and hydrogen-like ions (those with only one electron).

2. **Identifying Hydrogen-like Species**:
- Hydrogen-like species are those with a single electron. Examples include:
- Hydrogen (H) - 1 electron
- Helium ion (He⁺) - 1 electron (He has 2 electrons, but one is removed)
- Lithium ion (Li²⁺) - 1 electron (Li has 3 electrons, but two are removed)

3. **Analyzing the Given Options**:
- **Hydrogen (H)**: Applicable (1 electron).
- **Helium ion (He⁺)**: Applicable (1 electron).
- **Lithium ion (Li²⁺)**: Applicable (1 electron).
- **Bromine ion (Br⁺)**: Bromine has an atomic number of 35, meaning it has 35 electrons. When one electron is removed (Br⁺), it still has 34 electrons, which does not fit the criteria of being a hydrogen-like species.

4. **Conclusion**:
- The Bohr theory is not applicable for bromine ion (Br⁺) because it has more than one electron remaining after ionization.

### Final Answer:
The Bohr theory is not applicable for Br⁺ (Bromine ion).