What does the atomic number represent in an atom?

The atomic number is defined as the number of protons found in the nucleus of an atom. This fundamental property uniquely identifies an element and determines its position on the periodic table. Since atoms are electrically neutral, the atomic number also indicates the number of electrons in a neutral atom, but it is the protons that primarily determine the chemical properties and behavior of the element.

For example, hydrogen has an atomic number of 1, meaning it has one proton and one electron in its neutral state. In contrast, oxygen has an atomic number of 8, indicating it has eight protons (and also eight electrons in its neutral form). This relationship illustrates why the atomic number is so crucial in the study of chemistry and biology.

Understanding that the atomic number corresponds to the number of protons helps clarify concepts related to atomic structure, isotopes, and ions, allowing students to grasp how elements interact and combine in various biological processes.