Why does fluoriue show anomalous behaviour in its group ?

Explanation

The anomalous character of fluorine is due to
(a) its small size
(b) highest electronegativity
(c) low F-F bond dissociation energy and
(d) non-availability of d-orbitals in Valence shell.
Examples of anomalous character of fluorine.
(i) Most of the reactions of `F_2` are exothermic. It is due to small and strong bond formed by it with other elements.
(ii) It forms only one oxoacid, HOF while other halogens form a number of oxoacids.
(iii) HF is liquid at room temperature due to H-bonding, while other hydrogen halides are gases under similar conditions.