Reactivity of halogens

The non-metal in Group 7 – known as the – get less reactive as you go down the group. This is the opposite trend to that seen in the alkali metals in of the .

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. Produces iron(III) fluoride.
Chlorine	Reacts with heated iron wool very quickly, although not as quickly as fluorine does. Produces iron(III) chloride.
Bromine	Has to be warmed and the iron wool heated. The reaction is faster than that of iodine but slower than that of chlorine. Produces iron(III) bromide.
Iodine	Has to be heated strongly and so does the iron wool. The reaction is slow. Produces iron(III) iodide.

Halogen	Fluorine
Reaction with iron wool	Reacts with almost anything instantly. Very few scientists handle fluorine because it is so dangerous. Produces iron(III) fluoride.

Halogen	Chlorine
Reaction with iron wool	Reacts with heated iron wool very quickly, although not as quickly as fluorine does. Produces iron(III) chloride.

Halogen	Bromine
Reaction with iron wool	Has to be warmed and the iron wool heated. The reaction is faster than that of iodine but slower than that of chlorine. Produces iron(III) bromide.