A chemical equation is a set of symbols used to represent a chemical reaction. Equations show how atoms are rearranged as a result of a reaction, with reactants on the left-hand side and products on the right-hand side. For example, the formation of magnesium oxide when magnesium burns in oxygen is represented by

 

    2Mg + O₂ → 2MgO

 

position of a reversible The number of atoms of an element on the left-hand side of an equation must equal the number on the right.