Electron affinity: mind the sign
Electron affinity describes an energy change associated with adding an electron to a gaseous species. Sign conventions can differ between tables, so the definition must always be checked.
Core idea
Electron affinity describes an energy change associated with adding an electron to a gaseous species. Sign conventions can differ between tables, so the definition must always be checked.
Example
Comparing chlorine with a noble gas shows why the idea of simply 'wanting an electron' is insufficient: electronic structure and energy balance matter together.
Common trap
A formula or trend is useful only when its definition and conditions of use are clear.
Check yourself
Explain the phenomenon in your own words, then identify which quantity or mechanism you would use to quantify it.
Comparing chlorine with a noble gas shows why the idea of simply 'wanting an electron' is insufficient: electronic structure and energy balance matter together.