Classification of Elements and Periodicity in Properties - Result Question 19
####19. Which of the following represents the correct order of increasing electron gain enthalpy with negative sign for the elements $O, S, F$ and $Cl$ ?
[2005, 2010]
(a) $Cl<$ F $<$ O $<S$
(b) O $<$ S $<$ F $<Cl$
(c) F $<$ S $<$ O $<Cl$
(d) S $<$ O $<Cl<F$
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Solution:
- (b) $O<S<F<Cl$
Electron gain enthalpy of given elements are $-141,-200,-333$ and $-349 kJ mol^{-1}$ respectively.
Due to small size of atom, addition of an electron is not easy. This is the reason why the magnitude of electron gain enthalpy of oxygen and fluorine is less than that of sulphur and chlorine respectively.
