Some more elaborate method must be used to make combustion more efficient. Some elements, such as neon, are truly inert because they have 8 electrons in their outer shell and so have no need to form bonds. Elements with medium electro-negativities are not very reactive, but do react. Note that nitrogen is a diatomic molecule, so that before a nitrogen atom can bond with another atom the N-N bond must be broken. This happens at high temperatures, but at room temperature, it takes something special like a catalyst to break the N-N bond and allow a new compound to form.
Iron gives electrons to oxygen.
Thus it will not react with oxygen under ordinary conditions. Aluminum oxide forms a protective coating on the aluminum, preventing further oxidation. Ionic compounds have one and only one formula. Crude oil is a mixture of many different hydrocarbons of different size chains. In addition to all the different hydrocarbon molecules already present in crude oil, adding just one other atom such as O or Cl to hydrocarbon makes a totally different molecule.