Group 7: Halogens

The reactivity INCREASES UP the group (Fluorine is the most reactive). This also applies to electronegativity

Boiling points DECREASE UP the group (fluorine has the lowest boiling point). This is due to the increasing strength of Van Der Waals forces as the size and relative mass of the atoms decreases. This trend is also shown in physical states, Fluorine (Gas), Iodine (Solid)

The decrease in electronegativity down a group is due to the size of the atom, bigger atoms do not attract electron density as well as small atoms

When a halogen react, they gain an electron. This reactivity decreases down the group because the atoms get bigger, and therefore less electronegativity to draw the electron in.

A halogen will displace a halide from solution if the halide is lower than it in the periodic table

These displacement reactions can be used to identify which halogen (or halide) is present in a solution

Chlorine and Sodium Hydroxide make bleach

If you mix chlorine gas with dilute sodium hydroxide at room temperature, you get sodium chlorate(I) solution (NaClO in aqueous solution)

When you mix chlorine with water, it undergoes a reaction. You end up with a mixture of hydrochloric acid and chloric(I) acid (also called hypochlorous acid)

Chlorine + Water ---> HCl (aq) + HClO (aq)

HClO (aq) + Water ---> ClO- (aq) + H3O