Here's a breakdown:

* Cl: This is the chemical symbol for the element chlorine.

* 2: This subscript indicates that there are two chlorine atoms bonded together to form a molecule.

Chlorine gas is a yellowish-green gas with a pungent, suffocating odor. It is a very reactive element and is used in a variety of applications, including:

* Water purification: Chlorine is used to kill bacteria and other microorganisms in water.

* Bleach production: Chlorine is a key ingredient in bleach.

* Industrial processes: Chlorine is used in the production of many chemicals, including plastics, pesticides, and pharmaceuticals.

It is important to note that chlorine gas is toxic and can be dangerous if inhaled.