What does the atomic number represent in an element?

The atomic number of an element is defined as the number of protons present in the nucleus of an atom of that element. This fundamental characteristic is crucial because it uniquely identifies each element; for instance, hydrogen has an atomic number of 1, meaning it has one proton, while carbon, with an atomic number of 6, has six protons.

Additionally, in a neutral atom, the number of protons is equal to the number of electrons, which means that the atomic number also indirectly indicates the number of electrons in a neutral atom. However, the atomic number specifically refers to protons, making it a key identifier for the element itself and determining its position on the periodic table.

The average atomic mass, which refers to the average mass of an element's isotopes relative to the carbon-12 standard, and the number of neutrons, which can vary among isotopes of the same element, are distinct concepts and do not relate directly to the definition of atomic number. Thus, the atomic number is fundamentally tied to the number of protons, confirming why this answer is the most accurate.