a symbolic representation of a chemical reaction; reactants are represented on the left, and products on the right
2Na + 2H2O => 2NaOH + H2.
Method of writing the essential features of a chemical reaction using chemical symbols (or other agreed-upon abbreviations). By convention, reactants (present at the start) are on the left, products (present at the end) on the right. A single arrow between them denotes an irreversible reaction, a double arrow a reversible reaction. The law of conservation of matter (see conservation law) requires that every atom on the left appear on the right (the equation must balance); only their arrangements and combinations change. For example, one oxygen molecule combining with two hydrogen molecules to form two water molecules is written 2H2 + O2 2H2O. The dissociation of salt into sodium and chloride ions is written NaCl Na^+ + Cl^-. See also stoichiometry