For which one one of the following bohr model is not valid

Options

A. hydrogen atom
B. single ionised helium atom (`He^+`)
C. deuteron atom
D. single ionised neon atom (`Ne^+`)

Answer

To determine for which of the given options the Bohr model is not valid, we need to analyze each option based on the criteria that the Bohr model is applicable only to single electron systems.

### Step-by-Step Solution:

1. **Identify the Options**: We need to evaluate the following options:
- (A) Hydrogen atom (H)
- (B) Strongly Ionized Helium Atom (He+)
- (C) Deuteron atom (D)
- (D) Single Ionized Neon Atom (Ne+)

2. **Evaluate Hydrogen Atom (H)**:
- Hydrogen has one proton and one electron.
- It is a single electron system.
- **Conclusion**: Bohr model is applicable. (Not the answer)

3. **Evaluate Strongly Ionized Helium Atom (He+)**:
- Helium has two protons in its nucleus. In the case of He+, one electron is removed, leaving one electron.
- It is also a single electron system.
- **Conclusion**: Bohr model is applicable. (Not the answer)

4. **Evaluate Deuteron Atom (D)**:
- Deuteron consists of one proton and one neutron, with one electron revolving around the nucleus.
- It is a single electron system.
- **Conclusion**: Bohr model is applicable. (Not the answer)

5. **Evaluate Single Ionized Neon Atom (Ne+)**:
- Neon has an atomic number of 10, meaning it has 10 protons and 10 electrons in its neutral state (2-8 configuration).
- For Ne+, one electron is removed, leaving 9 electrons.
- Since there are still multiple electrons (9), it is not a single electron system.
- **Conclusion**: Bohr model is not applicable.

6. **Final Answer**: The Bohr model is not valid for the Single Ionized Neon Atom (Ne+).

### Summary:
The Bohr model is applicable to single electron systems. Among the options given, the only one that does not qualify as a single electron system is the Single Ionized Neon Atom (Ne+).