Most chemical reactions are written with the arrow pointing from left to right like this . There are special situations that call for the arrow to be written pointing from right to left like this . Since the arrow always points from reactants to products, the reactants would be on the right if the arrow is pointing this way. There are chemical reactions that begin to form products and the products break down into the original reactants. The small numbers to the lower right of chemical symbols.
Subscripts represent the number of atoms of each element in the molecule.
The large numbers in front of chemical formulas. Coefficients represent the number of molecules of the substance in the reaction. Just as subscripts of 1 are never written, coefficients of 1 are not written either. The subscript to the right of the parenthesis goes to all atoms inside. In each of the following equations, one of the reactant atoms is in bold type.