Fluorine is the most reactive of all the halogens. The difference in re activity between fluorine and chlorine is greater than that between chlorine and bromine. Table 22.4 shows that the F-F bond is considerably weaker than the Cl-Cl bond. The weak bond in F2 can be explained in terms of the lone pairs on the F atoms:
The small size of the F atom allows a close approach of the three lone pairs on each of the F atoms, resulting in a greater repulsion than that found in Cl2, which consists of larger atoms.
Hydrogen fluoride, HF, has a high boiling point (19.5) as a result of strong inter molecular hydrogen bonding, whereas all other hydrogen halides have much lower boiling points
Hydrofluoric acid is a weak acid, whereas all other hydrohalic acids (HCl, HBr and Hl) are strong acids.
Fluorine reacts with cold sodium hydroxide solution to produce oxygen difluoride as follows: