Which electronic configuration corresponds to a halogen?

Options

A. 2, 2
B. `2, 8, 2`
C. ` 2, 8, 1`
D. `2, 8, 7`

Explanation

To determine the electronic configuration that corresponds to a halogen, we can follow these steps:

### Step 1: Identify Halogens
Halogens are the elements found in Group 17 (or Group 7A) of the periodic table. The halogens include:
- Fluorine (F)
- Chlorine (Cl)
- Bromine (Br)
- Iodine (I)
- Astatine (At)

### Step 2: Understand Electronic Configuration
The electronic configuration of an element describes the distribution of electrons in its atomic orbitals. For halogens, we need to focus on their valence electrons, which are the electrons in the outermost shell.

### Step 3: General Electronic Configuration of Halogens
Halogens have a general electronic configuration of:
\[ ns^2 np^5 \]
This means that in their outermost shell (valence shell), they have:
- 2 electrons in the s subshell (ns²)
- 5 electrons in the p subshell (np⁵)

### Step 4: Calculate Total Valence Electrons
Adding the electrons in the valence shell:
- 2 (from ns²) + 5 (from np⁵) = 7 valence electrons

### Step 5: Example Electronic Configurations
- For Fluorine (F): 1s² 2s² 2p⁵ (total of 7 electrons in the outer shell)
- For Chlorine (Cl): 1s² 2s² 2p⁶ 3s² 3p⁵ (total of 7 electrons in the outer shell)
- For Bromine (Br): 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 4p⁵ (total of 7 electrons in the outer shell)
- For Iodine (I): 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 4p⁶ 5s² 5p⁵ (total of 7 electrons in the outer shell)

### Conclusion
The electronic configuration that corresponds to a halogen is generally of the form \( ns^2 np^5 \), indicating that halogens have seven electrons in their valence shell.

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