Final answer:
Counting atoms on both sides of a chemical equation ensures its balance, with the same number and types of atoms as reactants and products. Coefficients are adjusted to achieve this balance as needed, without changing the substance identities represented by their chemical formulas.
Step-by-step explanation:
When we count the number of atoms on both sides of a chemical equation, we ensure that the equation is balanced. A balanced equation has the same number and types of atoms on the reactant (left) and product (right) side. To balance a chemical equation, we can adjust the coefficients, which are the numbers placed in front of the compounds. For example, to balance the equation 2C + O2 → 2CO, we check that there are 4 carbon atoms and 4 oxygen atoms on both sides.
If the number of atoms doesn't match on both sides, we know the equation is not balanced and requires adjustment. For instance, if we have a hydrogen imbalance, such as in C(s) + H2 (g) → CH4 (g), we can balance it by adding a coefficient of 2 in front of H2, resulting in 4 hydrogen atoms on both sides, making the equation C(s) + 2H2 (g) → CH4 (g).