Group 7 (Halogens)

Group 7 of the periodic table is otherwise known as the Halogens, including elements such as Fluorine (F), Chlorine (Cl), Bromine (Br), Iodine (I), and Astatine (At).
As you move down Group 7, the reactivity of the Halogens decreases. This can be attributed to the increase in atomic radius and number of electron shells, causing a reduction in the attraction between the nucleus and the outer electrons. Therefore, they are less willing to gain extra electrons to achieve a stable full outer shell.
Despite this decrease in reactivity, the boiling and melting points of the Halogens increase as you move down the group. This can be linked to increased Van der Waals forces between larger molecules, requiring more energy to break these intermolecular forces.
Halogens exist as diatomic molecules in their elemental states. This means they are always found in pairs, for example Cl2, Br2, I2 etc, due to their willingness to share a pair of electrons to achieve stability.
Halogens show a trend in colour, becoming darker as you progress down the group. Fluorine is pale yellow, Chlorine is green-yellow, Bromine is red-brown, and Iodine is dark grey/purple.
The Halogens are all fairly electronegative with Fluorine being the most electronegative element in the Periodic Table.
They react with metals to form salts called halides. For example, sodium + chlorine –> sodium chloride.
They can also display displacement reactions amongst themselves, where a more reactive Halogen will displace a less reactive one from a solution of its salts.
Remember, Oxidation States of Halogens can vary from -1 to +7 depending on the specific compound. They achieve positive oxidation states when they form compounds with Oxygen or with other Halogens that are more electronegative.