Q.9 Explain anomalous behaviour of Fluorine with respect to
(i) Oxyacid (ii) Nature of hydrides
(iii) Electronegativity (iv) Electron gain enthalpy
Best answer
Answer: Fluorine differs from other halogens because of its very small size, highest electronegativity, low F–F bond enthalpy and absence of d-orbitals.
(i) Oxyacid: Fluorine forms only one oxyacid, HOF (hypofluorous acid), because it has no d-orbitals and is the most electronegative element; other halogens form several oxyacids (HOX, HXO2, HXO3, HXO4).
(ii) Nature of hydrides: HF is a liquid (b.p. 293 K) because of strong intermolecular hydrogen bonding, while HCl, HBr and HI are gases. HF is also the weakest acid among the hydrogen halides because of its high H–F bond enthalpy.
(iii) Electronegativity: Fluorine is the most electronegative element (4.0 on the Pauling scale) because of its small size, so it shows only the –1 oxidation state, whereas other halogens also show +1, +3, +5 and +7.
(iv) Electron gain enthalpy: The electron gain enthalpy of fluorine (–333 kJ mol–1) is less negative than that of chlorine (–349 kJ mol–1), because the added electron enters the small, compact 2p subshell and suffers strong repulsion from the electrons already present.
Log in or create a free account to answer this question.
