What does the atomic number of an element represent?

The atomic number of an element represents the total number of protons found in the nucleus of an atom of that element. This fundamental property is unique to each element and determines its identity. For instance, hydrogen has an atomic number of 1 because it has one proton, while carbon has an atomic number of 6 due to its six protons.

The atomic number is significant because it not only identifies the element but also influences its chemical behavior through the arrangement of electrons in its electron shells. While the number of neutrons and the sum of protons and neutrons (which gives the atomic mass) are important for understanding the isotopes and mass of an element, they do not define what the element is.

Additionally, the number of electrons in the outer shell pertains to the element's reactivity and bonding properties but does not affect the definition of the atomic number itself. Hence, the atomic number is solely based on the number of protons.