Hello. I've learn that fire is chain-reaction process when burning materials are surrounded by oxygen with enough amount and they're heated exceeding some ignition point. That point is nothing but the temperature above which oxidation between material and oxygen begins. Then during oxidization, heat is realized so chain-reaction starts. Here I would like to know atomic transition of this oxidation. Specifically, I want to know how heat is realized when electron from material transfers to the oxygen. Is it due to that original energy level of the electron higher than occupied level in oxygen? Does electron occupy outermost orbit of oxygen? Is oxidization all heat-realize process?