Loss of electrons from an atom, ion, or molecule. Always paired with reduction (gain of electrons) in redox reactions -- one cannot occur without the other.
redox
oxidation: loss of electrons, increase in oxidation state
reduction: gain of electrons, decrease in oxidation state
oxidizing agent: accepts electrons (is itself reduced)
reducing agent: donates electrons (is itself oxidized)
biological oxidation
cellular respiration: glucose is oxidized to CO2, oxygen is reduced to H2O, releasing ~36 ATP
electron transport chain: sequential redox reactions in mitochondria, the final step of aerobic metabolism
antioxidants: molecules that donate electrons to neutralize free radicals (reactive oxygen species)
chemical oxidation
rusting: iron + oxygen + water -> iron oxide (Fe2O3)
combustion: rapid oxidation releasing heat and light
bleaching: oxidizing agents (chlorine, hydrogen peroxide) break chromophores
electrochemistry
Batteries convert chemical energy to electrical energy via separated redox half-reactions. Electrolysis uses electrical energy to drive redox reactions in reverse.
connections
combustion is violent oxidation. fermentation avoids oxidation by operating anaerobically. photosynthesis reverses oxidation by reducing CO2 back to sugar using light energy.