The production of ATP from ADP and inorganic phosphate through the F0 - F1 particles in mitochondria is called oxidative phosphorylation.
As electrons pass from one electron carrier to the other through Complex I to Complex IV in the electron transport chain (ETC), the electrons are coupled to the enzyme ATP synthase in F1 particles for the production of ATP from ADP.
As electrons are transported from one molecule of NADH+ + H through ETC three pairs of protons are transported from the outer mitochondrial membrane to the matrix thereby generating 3 ATP molecules.
As electrons pass from one molecule of FADH2 two pairs of protons are released which in turn generates two molecules of ATP.
So,ATP is synthesised in oxidative phosphorylation and O2 is reduced to H2O as electrons get transferred from various electron carriers to molecular oxygen.