Chlorine (cl) Bromine (Br) and Iodine (I) - only ones we have to study.
They are called halogens as they all exist as diatomic molecules. They are non metals and are very reactive elements.
As you go down the group the elements become less volatile. This is becuase as you go down the group the elements gain more electrons which increases the van der waals forces thus being less reactive.
Chlorine is a GREENISH/YELLOW colour gas
Bromine is DARK RED liquid with a DARK RED/BROWN vapour
Iodine is a shiny GREY/BLACK crystaline solid, however when heated gently it sublimes ( which means it goes straight from solid to vapour state) to a PURPLE colour vapour.
Chlorine is a gas, Bromine is…