The Group 7 elements are known as the halogens. They are reactive non-metals and are always found in compounds with other elements. Chlorine, bromine and iodine are all halogens.
The non-metal elements in Group 7 - known as the halogens - get less reactive as you go down the group. This is the opposite trend to that seen in the alkali metals in Group 1 of the periodic table.
Fluorine is the most reactive element of all in Group 7.
You can see the trend in reactivity if you react the halogens with iron wool.
| Halogen | Reaction with iron wool |
|---|---|
| Fluorine | Reacts with almost anything instantly. Very few scientists handle fluorine because it is so dangerous. |
| Chlorine | Reacts with heated iron wool very quickly. |
| Bromine | Has to be warmed and the iron wool heated. The reaction is faster. |
| Iodine | Has to be heated strongly and so does the iron wool. The reaction is slow. |