Coefficients

This is the big number in front of a chemical formula. This number tells how many groups of that formula you have.

3 CO₂

The THREE in front of CO₂ is the coefficient.

Subscripts

The small number after the chemical formula. It only belongs to the element that it immediately follows and counts the amount of that element.

3 CO₂

The TWO after the chemical formula is the subscript.

Reactants

In a chemical equation, the reactants are on the left side of the arrow.

In this example

2Mg + O₂ --> 2MgO

• the reactants are 2Mg + O₂

• Reactants are always on the left.

Products

In a chemical equation, the products are on the right side of the arrow.

In this example

2Mg + O₂ --> 2MgO

• the product is 2MgO

• The products are always on the right.

Law of Conservation of Mass

Matter can not be created or destroyed, it only gets rearranged. In a chemical equation, the left side must be equal to the right side. The Reactants are equal to the Products.