Why is ATP synthesis in the electron transport chain known as oxidative?

ok i understand that oxygen is essential because it combines with hydrogen atoms to create water .... Without oxygen ,the electron transport chain would stop because there would be no oxygen for the electrons +protons which form =hydrogen atoms to combine to make water so the electrons.So would ATP synethesis eventually stop because the H+ concentration in the mitochondrial matrix would build up and then the protons would have to go back up the concetration gradient (but surely by doing this Still Atpase can catalyse ATP synthesis)...i'm so confused may some one please explain...thank you