What does the term 'atomic number' represent?

Neutrons are neutral particles found in the nucleus alongside protons, but they do not define the atomic number. Instead, the number of neutrons can vary within atoms of the same element, leading to different isotopes. Therefore, neutrons do not contribute to the atomic number, which is solely based on protons.

Electrons are negatively charged particles that orbit the nucleus and play a role in chemical bonding and reactivity. While the number of electrons in a neutral atom is equal to the number of protons, the atomic number specifically refers to protons, not electrons. Variations in electron counts can lead to ionization but do not alter the atomic number.

Isotopes are variants of a given element that differ in neutron count, resulting in different mass numbers. The atomic number, however, is constant for an element and does not reflect the number of isotopes. An element may have multiple isotopes, but this does not change its atomic number, which remains determined by the number of protons.