What does the atomic number of an element represent?

The atomic number of an element specifically represents the number of protons present in the nucleus of an atom of that element. This fundamental characteristic is unique to each element and determines the element's identity in the periodic table. For example, hydrogen has an atomic number of 1, indicating it has one proton, while carbon has an atomic number of 6, indicating it has six protons.

This proton count also establishes the chemical properties of the element, as it influences how atoms interact and bond with others. The atomic number is crucial because it is utilized to organize the periodic table in increasing order, allowing scientists and chemists to predict element behavior based on their position. The number of electrons in a neutral atom typically matches the number of protons, but it is the protons alone that define the atomic number. The other options do not correctly describe what the atomic number signifies. For instance, neutrons are involved in the atomic mass but do not factor into the atomic number, while atomic mass units provide measurements of mass rather than identifying elements.