Volatility decreases down group 7.

This is because the molecules contain increasing numbers of electrons which results in stronger induced dipole-dipole forces which require increasing amounts of energy to overcome.

Volatility is the tendency to turn into a gas, so less volatile substances have higher boiling points.

The bond strength of halogen molecules generally decreases going down the group.

This is because the attraction between the halogen nuclei and the shared pair of electrons in the covalent bond gets weaker as the atomic radius and the amount of electron shielding both increase.

Fluorine is an exception, with the F-F bond being weaker than the Cl-Cl bond due to greater electron-electron repulsion between the lone pairs on the small fluorine atoms.

Electronegativity decreases as we move down group 7.

This is due to the increasing atomic radius, which leads to greater shielding and a weaker attraction for bonding electrons.

Fluorine is a pale yellow gas at room temperature.

Iodine is a dark grey solid at room temperature.

Solid iodine readily sublimes into a purple gas.

Chlorine is a green gas at room temperature.

Bromine is a red-brown liquid at room temperature.

Halogens exist as diatomic molecules.

This means they exist in pairs of atoms, like F₂, or Cl₂.