What determines the identity of an element?

The identity of an element is fundamentally determined by the number of protons in its nucleus. This number, known as the atomic number, assigns a unique identity to each element in the periodic table. For example, an atom with one proton is hydrogen, while an atom with six protons is carbon.

While neutrons and electrons are important for the mass of an atom and its charge respectively, they do not determine the elemental identity. The number of neutrons can vary within atoms of the same element, resulting in different isotopes, while the number of electrons can change based on ionization processes, affecting the atom's overall charge but not its elemental classification. Quarks are the fundamental particles that combine to form protons and neutrons, but they are not used to define an element's identity in the context of chemistry or atomic structure. Thus, recognizing the role of protons is essential for understanding the identity of elements.