electron affinity

Question

Which element has the highest electron affinity?

RankGuru · Accepted Answer

This is a classic exception in periodic trends. 
- **Fluorine ($F$)** is the most electronegative, so one might expect it to have the highest electron gain enthalpy (electron affinity).
- However, **Chlorine ($Cl$)** actually has a higher (more negative) electron affinity value.
- **Reason**: Fluorine's atom is extremely small. When an electron is added to the small $2p$ subshell of $F$, it experiences significant **electron-electron repulsion** from the electrons already present. 
- Chlorine's $3p$ subshell is larger, accommodating the new electron with less repulsion.

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electron affinity

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More electron affinity Practice Questions

Which element has the most exothermic (most negative) electron affinity?