## Chemistry: Molecular Approach (4th Edition)

$_{Z}^{A}\text{X}$ and $\text{X-}A$
The isotope of a substance is represented as follows: $_{Z}^{A}\text{X}$ Here, $\text{X}$is the chemical symbol of the element, $A$ is the mass number and $Z$ is the atomic number. Isotopes are also represented as: $X-A$ where X represents chemical symbol and A represents mass number of the isotopes.