Chemistry - PERIODIC TABLE Question with Solution | TestHub

The amount of energy released when an electron is added to an isolated gaseous atom to produce a monovalent anion is called electron gain enthalpy. Electron affinity value generally increase on moving from left to right in a period however there are exceptions of this rule in the case of those atoms which have stable configuration. These atoms resist the addition of extra electron, therefore the low value of electron affinity $\underset{-1.48}{\mathrm{O}}<\underset{-2.0}{S}<\underset{-3.6}{F}<\underset{-3.8}{\mathrm{Cl}}$ On the other hand $\mathrm{Cl}$, because of its comparatively bigger size than $\mathrm{F}$, allow the addition of an extra electron more easily.