How do fluorine's physical properties differ from those of bromine and iodine?

Fluorine’s physical properties differ significantly from those of bromine and iodine due to its position as the lightest and most electronegative halogen.12

Physical State and Appearance

At room temperature and atmospheric pressure, fluorine exists as a faintly yellow gas. In contrast, bromine is a reddish-brown liquid, and iodine is a nearly black solid that forms glittering crystals.1234

Boiling and Melting Points

Fluorine has the lowest melting point (–219.62 °C) and boiling point (–188.12 °C) of the group. These values increase markedly with atomic number: bromine melts at –7.2 °C and boils at 58.8 °C, while iodine has a much higher melting point of 113.7 °C and a boiling point of 184.3 °C. This trend is driven by increasing molecular size and polarizability, which strengthen intermolecular London dispersion forces in the heavier halogens.25

Density and Solubility

Fluorine is the least dense of the three, while iodine is the most dense. Furthermore, unlike bromine and iodine, which can be dissolved in various solvents, fluorine reacts directly with water. Additionally, fluorine is the least polarizable halogen, whereas iodine is the most polarizable.5234