Atomicity of Halogens

The atomicity of an element refers to the number of atoms present in a molecule of that element. In the case of halogens, the correct answer is option 'B', which means they exist as diatomic molecules.

Explanation:

1. Definition of Halogens:
Halogens are a group of elements in the periodic table that includes fluorine (F), chlorine (Cl), bromine (Br), iodine (I), and astatine (At). They belong to Group 17 or Group VIIA of the periodic table.

2. Diatomic Molecules:
Diatomic molecules are molecules that consist of two atoms of the same element bonded together. In the case of halogens, they exist as diatomic molecules, meaning they are made up of two atoms of the same halogen element bonded together.

3. Molecular Formulas of Halogens:
The molecular formulas of halogens are as follows:
- Fluorine (F): F2
- Chlorine (Cl): Cl2
- Bromine (Br): Br2
- Iodine (I): I2
- Astatine (At): At2

4. Explanation of Diatomic Nature:
Each halogen atom has an electron configuration that requires one additional electron to achieve a stable configuration. In order to achieve this stable configuration, halogens readily form covalent bonds with another halogen atom, sharing one electron from each atom. This results in the formation of a diatomic molecule.

5. Example:
For example, chlorine (Cl) has an electron configuration of 2, 8, 7. It requires one additional electron to achieve the stable configuration of argon (2, 8, 8). Two chlorine atoms can come together and share one electron each, forming a covalent bond and resulting in the formation of a chlorine molecule (Cl2).

Therefore, the atomicity of halogens is diatomic, meaning they exist as diatomic molecules consisting of two atoms of the same halogen element bonded together.