2.2 - Group 7

The elements in group 7 are known as the halogens. These are fluorine, chlorine, bromine, iodine and astatine

These elements are non-metals that are poisonousreact with metals to form salts

All halogens have similar reactions as they each have seven electrons in their outermost shell

Yellow gas

yellow gas

Red - brown liquid

purple black solid

Very reactive poisonous gas

Reactive poisonous and dense gas

Dense red - brown volatile liquid

Shimmery crystalline solid sublimes to form a purple vapour

The melting and boiling points of the halogens increase as you go down the group This is due to increasing intermolecular forces as the atoms become larger, so more energy is required to overcome these forces

The colours of the halogens also change as you descend the group - they become darker

The halogens decrease in reactivity moving down the group, but they still form halide salts with some metals including iron The rate of reaction is slower for halogens which are further down the group such as bromine and iodine

A halogen displacement reaction occurs when a more reactive halogen displaces a less reactive halogen from an aqueous solution of its halide

The solution becomes orange as bromine is formed or The solution becomes brown as iodine is formed Chlorine is above bromine and iodine in group 7 so it is more reactive Chlorine will displace bromine or iodine from an aqueous solution of the metal halide:

The metal ion in a halogen reaction does not do anything doesn’t react.

Reactivity of group 7 non-metals decreases as you go down the group As you go down group 7, the number of shells of electrons increases, the same as with all other groups Halogensform negative ions This means that the increased distance from the outer shell to the nucleus as you go down a group makes the halogens become less reactiveless atraction between the nucleus and the shells Fluorine is the smallest halogen, which means its outermost shell is the closest to the positive nucleus of all the halogen Therefore, the ability to attract an electron is strongest in fluorine making it the most reactive As you move down the group, the forces of attraction between the nucleus and the outermost shell decreases This makes it harder for the atoms to gain electrons as you descend the group Therefore, the halogens are less reactive the further down the group you go

When oxidation and reduction occours

the more reactive element acts as the oxidising agent it takes electrons away from the less reactive element reducing itself