Q. What are the Physical Properties of Halogens?
Ans.
The halogens exist as diatomic molecules held together by a single bond. Reactivity becomes less as you move down the halogen column in the periodic table. This is due to the increasing size of the atoms. The internal, positively charged nucleus becomes increasingly shielded by the greater number of surrounding electrons.
As size increases, the melting and boiling points of the halogens increase down the group. Thus, fluorine and chlorine are gases. Bromine, a volatile liquid, is a gas just above room temperature. Iodine is a volatile solid.
A safety note: The halogens are poisonous. All halogens have a characteristic "bleachy" smell that will irritate your nose and throat. Bromine attacks your skin and can produce painful burns. Avoid contact with the halogens, and avoid smelling their vapors.