The anomalous properties of fluorine are as follows :
- Fluorine has the highest reactivity among other halogens.
- Fluorine forms strong hydrogen bonding in its hydrides unlike other halogens.
- HF is a liquid while other hydrogen halides are gases at room temperature.
- HF is a weak acid while other haloacids are strong acids.
- Fluorine shows only one oxidation state – 1 while all other halogens show variable oxidation states like -1, +1, +3, +5 and + 7.
- Fluorine has the highest electronegativity but less negative electron gain enthalpy than chlorine.
- The compounds of fluorine have higher ionic character than other halogens.
- Fluorine has no tendency to form polyhalide ion whereas other halogens form polyhalide ions like, Cl3-, Br3- and I3-.
- Fluorine unlike other halogens when reacts with water and produces O2 and O3. 2F2 + 2H2O → 4HF + O2 ; 3F2 + 3H2O → 6HF + O3
- Fluorine shows much higher values of ionisation enthalpy, electronegativity and standard electrode potentials compared to the other halogens.
- Fluorine shows much lower values of ionic and covalent radii, melting and boiling points and electron gain enthalpy than expected.
- Fluorine forms only one oxoacid HOF, while the other halogens form a number of oxoacids.
