What does the atomic number of an element represent?

The atomic number of an element is defined as the number of protons located in the nucleus of an atom. This numerical value is fundamental because it uniquely identifies an element and determines its position on the periodic table. Since each element has a distinct atomic number, this value essentially defines the chemical properties of the element and dictates its behavior during chemical reactions.

The atomic number also relates to the number of electrons in a neutral atom, given that the number of protons equals the number of electrons. However, the atomic number specifically refers to protons, making it the key identifier for the element itself. Meanwhile, the number of neutrons can vary among isotopes of the same element, and the total mass of an atom is a combination of both protons and neutrons, so these aspects do not define the atomic number.