Question
Explain the electron gain enthalpy of group 16 elements.
✓
Answer
- Electron gain enthalpy (or electron affinity) is the energy released when an electron is added to the valence shell of a gaseous atom forming gaseous ion.
$M _{( g )}+ e ^{-} \longrightarrow M ^{+}{ }_{( g )}+$ energy
More the energy released more is electron gain enthalpy or electron affinity. - Group 16 elements have high values for electron gain enthalpy. On moving down the group, electron gain enthalpy decreases from S to Po.
- Oxygen has less negative electron gain enthalpy, due to high electronegativity, low atomic size and high electron density so that the incoming electron is repelled.
- Electron gain enthalpy of the elements decreases down the group due to successive decrease in electronegativity and nuclear attraction and increase in atomic size.
Element S Se Te Po o Electron gain enthalpy $kJ / mol$ $-200$ $-195$ $-190$ $-174$ $-141$
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