Balance

The law of conservation of mass states that matter cannot be created nor destroyed. There are no more or less atoms at the end of a chemical reaction than there were at the beginning. To balance a chemical equation, every element must have the same number of atoms on each side of the equation.

${\displaystyle Na}$ is not a balanced element. To balance ${\displaystyle Na}$, multiply ${\displaystyle NaHC{O}_3}$ from the left side by ${\displaystyle 2}$.

${\displaystyle H}$ is a balanced element because there is the same number of atoms of ${\displaystyle H}$ in each side of the equation.

${\displaystyle C}$ is a balanced element because there is the same number of atoms of ${\displaystyle C}$ in each side of the equation.

${\displaystyle O}$ is a balanced element because there is the same number of atoms of ${\displaystyle O}$ in each side of the equation.