Chemistry Group VII - The Halogens

The halogens are a group of reactive non-metals that share similar properties, with gradual changes down the group. They exist as diatomic molecules, meaning they consist of two atoms bonded together.

The strength of the van der Waals forces between halogen molecules increases down the group. This is because larger molecules have more electrons, leading to stronger intermolecular attractions.

Fluorine (F2) is a yellow gas, Chlorine (Cl2) is a green-yellow gas, Bromine (Br2) is a reddish-brown liquid, and Iodine (I2) is a grey-black solid. These are their physical states at room temperature.

The halogens become less soluble in water as you move down the group. This is because the strength of the van der Waals forces between halogen molecules increases, making it harder for water molecules to break them apart.

Halogens can react with sodium hydroxide to form different products depending on the concentration and temperature. In cold, dilute NaOH, halides and hypohalites (containing XO-) are formed. In hot, concentrated NaOH, halides and halates (containing XO3-) are formed.

Chlorine reacts with water to form chloride ions (Cl-) and chlorate(I) ions (ClO-). This reaction is an example of disproportionation, where the same element is both oxidized and reduced.

The oxidizing ability of halogens decreases down the group. This means that a halogen higher up in the group can displace a halogen lower down in the group from its solutions.

Solid halides, like sodium chloride, react with concentrated sulfuric acid, but the reaction depends on the halide ion. Fluoride and chloride ions form hydrogen halides, while bromide and iodide ions undergo oxidation to form bromine and iodine, respectively.