Question

Discuss four points of anomalous behavior of fluorine.

Answer 1

Due to small atomic size, high electronegativity and the absence of inner d-orbitals, fluorine shows anomalous behaviour. Some of the properties in which fluorine differs from rest of group 17 elements are listed below:

1. Ionisation enthalpy, electronegativity, electrode potential all are higher for fluorine than expected trends shown by other halogens.
2. Ionic radii, covalent radii, and negative electron gain enthalpy are quite lower than expected.
3. Most of the reactions of fluorine are exothermic due to the short and strong bond formed by it with other elements.
4. It forms only one oxoacid (HOF) while other halogens form a number of oxoacids.
5. Hydrogen fluoride is a liquid (b.p. 293 K) due to strong hydrogen bonding while other hydrogen halides are gases.
6. Fluorine exhibits –1 oxidation state only. However, Cl, Br and I exhibit +1, +3, +5 and +7 oxidation states as well.