What is an element defined by in terms of its atomic structure?

An element is defined by its atomic structure, particularly by the number of protons it contains in its nucleus. This number, known as the atomic number, is unique to each element and determines the identity of the element. For instance, hydrogen has one proton, while carbon has six protons. This atomic number not only categorizes the element but also influences its chemical behavior and properties.

The number of neutrons contributes to the identity of an isotope of an element but does not define the element itself. While the number of electrons can influence the charge and stability of an atom, it is the protons that define the element in terms of its position on the periodic table and its fundamental characteristics. The chemical properties of an element are indeed linked to its atomic structure and the number of protons, but they are not used to define the element itself as clearly as the atomic number does.