Out of the elements with atomic numbers given below which one would be a halogen

Options

A. 25
B. 35
C. 45
D. 55

Explanation

To determine which of the given atomic numbers corresponds to a halogen, we need to understand the electronic configuration of halogens. Halogens belong to Group 17 of the periodic table, and their general electronic configuration is \(ns^2np^5\), where \(n\) is the principal quantum number.

### Step-by-Step Solution:

1. **Identify the Atomic Numbers**: The question does not specify the atomic numbers, but we will assume we are checking atomic numbers 25, 35, 45, and 55 based on the video transcript.

2. **Determine the Electronic Configuration**:
- For each atomic number, we will write the electronic configuration to find the valence shell configuration.

3. **Calculate the Electronic Configuration for Each Atomic Number**:
- **Atomic Number 25**:
- Configuration: \(1s^2, 2s^2, 2p^6, 3s^2, 3p^6, 4s^2, 3d^{10}\)
- Valence Configuration: \(4s^2 3d^{10}\) (not a halogen)

- **Atomic Number 35**:
- Configuration: \(1s^2, 2s^2, 2p^6, 3s^2, 3p^6, 4s^2, 3d^{10}, 4p^5\)
- Valence Configuration: \(4s^2 4p^5\) (this matches \(ns^2np^5\), so this is a halogen - Bromine)

- **Atomic Number 45**:
- Configuration: \(1s^2, 2s^2, 2p^6, 3s^2, 3p^6, 4s^2, 3d^{10}, 4p^6, 5s^2, 4d^{10}\)
- Valence Configuration: \(5s^2 4d^{10}\) (not a halogen)

- **Atomic Number 55**:
- Configuration: \(1s^2, 2s^2, 2p^6, 3s^2, 3p^6, 4s^2, 3d^{10}, 4p^6, 5s^2, 5p^6\)
- Valence Configuration: \(5s^2 5p^6\) (not a halogen)

4. **Conclusion**: The only atomic number that corresponds to a halogen is **35**, which is Bromine.

### Final Answer:
The halogen among the given atomic numbers is **Atomic Number 35 (Bromine)**.