Here's why:
* Bromine is a halogen: Halogens are highly reactive elements that exist as diatomic molecules in their elemental form. This means they naturally form pairs of the same atom.
* Bromine is a gas at room temperature: While bromine is a liquid at room temperature, it readily evaporates and exists as a gas.
So, when you have bromine gas, you have individual Br2 molecules moving around.
