Group 7

A reaction in which a substance is simultaneously reduced and oxidised

The tendency of an atom to attract a bonding pair of electrons

Oxidising ability is the ability to act as an oxidising agent. The oxidising ability of the halogens decreases down the group. This is because down the group the atoms get larger so the electrons are less strongly attracted to the nucleus so it is harder to gain an electron

Reducing ability is the ability to act as a reducing agent. The reducing ability, or reducing power, of the halides increases down the group. This is because to act as a reducing agent the halide needs to lose an electron. As you go down the group it is easier for a halide to lose an electron because the attraction from the outer electron and nucleus decreases due to increased shielding and an increasing ionic radius

A chemical reaction in which one element replaces another element in a compound. A halogen will displace a halide from solution if the halide is below it in the periodic table

pale yellow gas

greenish reactive gas

red liquid

shiny grey solid sublimes purple gas

Increase down the group

As one goes down the group the electronegativity of the elements decreases. As one goes down the group the atomic radii increases due to the increasing number of shells. The nucleus is therefore less able to attract the bonding pair of electrons.

decreases down the group

Cl2(g) + H2O (l) ⇌ HClO (aq) + HCl (aq)