In an experiment to determine the empirical formula of magnesium oxide, a student weights an empty crucible then adds a strip of magnesium metal and reweighs the crucible. The crucible and magnesium are heated with a burner flame, which ignits the magneisum and forms a grey-white solid. After cooling, the crucible and solid are reweighed and the date are analyzed to given an empirical formula of Mg5O4. Which could account for the observed Mg5O4 results rather than the expected MgO?