2.7.2e: make predictions about fluorine and astatine and their compounds based on the trends in the physical and chemical properties of halogens

Reactivity:

• decreases as you go down the group
• halogen atoms are trying to gain one more electron to have a full outer shell, so the closer the outer electrons are to the nucleus (smaller atomic radius), the more reactive the halogen

Electronegativity:

• decreases as you go down the group
• the smaller the atomic radius, the more attraction the nucleus can exert on electrons

Ionisation energy:

• decreases as you go down the group
• more shells = less attraction of the outer electrons, so they can be more easily removed

Melting/boiling points:

• increases as you go down the group
• all are simple molecules with weak van der Waals forces, so the bigger atoms are more polarisable and have more electrons, allowing them to have stronger van der Waals forces