Give two examples to show the anomalous behaviour of fluorine.

Anomalous behaviour of fluorine

(i)    It forms only one oxoacid as compared to other halogens that form a number of oxoacids.
(ii)    Ionisation enthalpy, electronegativity, and electrode potential of fluorine are much higher than expected.

The anomalous behaviour of fluorine is due to its: 

1. Small size 

2. highest electronegativity 

3. low F-F bond dissociation enethalpy 

4. non-availability of d-orbitals in its valence shell. 

The two examples are: 

1. Due to non-availability of d-orbitals in its valence shell, fluorine cannot expand its octet, therefore, shows only -1 oxidation state while all other halogens due to the presence of d-orbitals shows positive 

 2. Due to its small size, the three lone pair of electrons on each F atom in F – F molecule, repel the bond pair. As a result, F – F bond dissociation energy is lower than that of Cl – Cl bond.