Introduced to this concept in AP Chemistry

What is it? §

• Measure of the change in energy of an atom when an e${}^{-}$ is added to it
• If adding e${}^{-}$ makes atom more stable, energy is given off (exothermic)
• If adding e${}^{-}$ makes atom less stable, energy must be added (endothermic)
• Take the value of the free atom and the result and if the energy is lower energy it has released energy

F (g) + e${}^{-}$ -> F${}^{-}$ (g) $△$ H = -328 kJ/mol O (g) + e${}^{-}$ -> O${}^{-}$ (g)

As halogens gain electrons they become more stable

How to calculate it §