1. 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.
More the energy released more is electron gain enthalpy or electron affinity.
2. Group 16 elements have high values for electron gain enthalpy. On moving down the group, electron gain enthalpy decreases from S to Po.
3. 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.
4. 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 |
-200 |
-195 |
- |
- |
-141 |
| enthalpy kJ/mol |
|
|
190 |
174 |
|
