Question

Compare the elements of group 15 with those of group 16 in relation to the following property:

Electron affinity

Answer 1

1. Group 15 elements have the electronic configuration (ns² np³), meaning a half-filled p-subshell, which is more stable and symmetrical.
2. Due to this stability, group 15 elements have less tendency to gain an extra electron, resulting in less negative electron affinity values.
3. Group 16 elements have the configuration (ns² np⁴), with one more electron than the half-filled stable state.
4. This makes group 16 elements more likely to accept an electron, generally showing higher (more negative) electron affinity than group 15 elements.
5. However, oxygen (in group 16) has a less negative electron affinity compared to sulphur because its small atomic size causes higher electron-electron repulsions when gaining an electron.
6. Moving down the groups, electron affinity generally becomes less negative due to increasing atomic size and decreasing effective nuclear charge.