What does the atomic number of an element represent?

The atomic number of an element is defined as the number of protons found in the nucleus of an atom. This number is fundamental because it determines the identity of the element. For example, any atom that has an atomic number of 6 is carbon, while an atomic number of 8 signifies oxygen. The atomic number also influences the chemical properties of the element, as it affects how atoms interact with each other during chemical reactions.

While the number of electrons in a neutral atom is equal to the atomic number, this characteristic specifically refers to the neutral state of the atom and does not reflect the atomic number itself. Additionally, the atomic number does not represent the number of neutrons or the mass of the atom, which are separate concepts within atomic theory. Neutrons, which contribute to the atomic mass but are not involved in defining the element, can vary in number within atoms of the same element, resulting in isotopes. The mass of the atom, which accounts for both protons and neutrons, is referred to in context to atomic mass, but not the atomic number. Thus, the atomic number is a clear, defining characteristic of an element based solely on its proton count.