Question

how does 2Mg + O2(two atoms of oxygen)becomes magnesium oxide(2MgO)?

Answer 1

During a chemical reaction, rearrangement of atoms in the reactants takes place to give products.The molecular oxygen becomes atomic oxygen and combines with Mg by gaining two electrons from Mg atom which looses to electrons. Thus, 2 Mg atoms combine with two O atoms to give 2MgO.