Reactions of Halogens and Halides

Halogens (Group 7 elements) are highly reactive non-metals due to their ability to accept an electron to achieve a stable full outer shell.
Fluorine is the most reactive of all halogens because it has the smallest size and highest electronegativity, and iodine is the least reactive because it has the largest size and lowest electronegativity.
The physical properties of halogens, for instance, boiling points and colour, increase down the group due to an increase in the number of electron shells and hence, increased van der Waals forces.
Redox reactions involving halogens are characterised by changes in the oxidation number. The halogen acts as an oxidising agent as it is reduced (gains electron), thus it’s important to understand the concept of oxidation states and redox potentials.
For halide displacement reactions, a more reactive halogen can displace a less reactive halide from solutions of its salts. This follows a pattern in the Group 7 elements.
The addition reaction of a halogen to an alkene is also key. In this reaction, a halogen molecule reacts with a carbon-carbon double bond of an alkene, resulting in a dihalogenoalkane.
Halogens can also react to form covalent diatomic molecules, such as Cl2 or I2. This requires a combination of the same two halogen atoms.
Halide ions can be identified using silver nitrate solution. The halides form a precipitate of different colours with silver ions, which can be used to identify the specific halide ion.
All of the halogens form halide ions which have different solubilities in water and ammonia, and these characteristics can be used to distinguish between them in laboratory tests.
Lastly, it is beneficial to practise identifying and predicting the products of common reactions involving halogens, such as the reaction of a halogen with sodium hydroxide or hydrogen.