Question

Which one of the following arrangements represents the correct order of electron gain enthalpy (with negative sign) of the given atomic species

• A. Cl<F<S<O
• B. O<S<F<Cl
• C. S<O<Cl<F
• D. F<Cl<O<S

Answer 1

The correct option is B

O<S<F<Cl

Halogens have very high electron affinities. It may be noted that the electron affinity of fluorine is unexpectedly low (<Cl). This may perhaps be due to the small size of the F atom. The values of electron gain enthalpies for Cl,F, S and O are respectively 349, 333, 200 and 142 kJ/mole hence correct order is Cl>F>S>O.