Halogen elements are those which are

Options

A. diatomic and form `X^(- -)` ions
B. monatomic and form `X^(- -)` ions
C. diatomic and form `X^(- )` ions
D. monoatomic and form `X^(-)` ions

Explanation

To answer the question "Halogen elements are those which are?", we will follow a systematic approach to identify the characteristics of halogens.

### Step-by-Step Solution:

1. **Identify the Group**:
Halogens are elements found in Group 17 of the periodic table. This group includes the elements: Fluorine (F), Chlorine (Cl), Bromine (Br), Iodine (I), and Astatine (At).

**Hint**: Remember that halogens are located in Group 17, which is also known as Group VIIA in some periodic tables.

2. **Valence Electrons**:
Halogens have 7 valence electrons in their outermost shell. The general electron configuration for halogens can be represented as NS²NP⁵, where N is the principal quantum number.

**Hint**: Focus on the number of valence electrons; halogens are one electron short of a complete octet.

3. **Stability and Reactivity**:
To achieve stability, halogens tend to gain one electron to complete their octet. This can occur in two ways:
- **Formation of Anions**: Halogens can gain an electron to form negatively charged ions (X⁻). For example, Chlorine can gain one electron to become Cl⁻.
- **Formation of Diatomic Molecules**: Halogens can also share electrons with another halogen atom to form diatomic molecules (X₂). For example, two Chlorine atoms can bond to form Cl₂.

**Hint**: Consider the two ways halogens achieve stability: gaining an electron or sharing electrons.

4. **Diatomic Nature**:
Halogens are commonly found as diatomic molecules in their elemental form (e.g., F₂, Cl₂, Br₂, I₂). This diatomic nature is crucial for their stability.

**Hint**: Remember that halogens exist as diatomic molecules in nature, which is a key characteristic.

5. **Conclusion**:
Based on the above points, we can conclude that halogen elements are characterized by their ability to form diatomic molecules and their tendency to form anions (X⁻) when they gain an electron.

### Final Answer:
Halogen elements are those which are diatomic and can form X⁻ ions.