What does the atomic number of an element indicate?

The atomic number of an element is a fundamental concept in chemistry and physics, representing the number of protons present in the nucleus of an atom of that element. This is crucial because the atomic number defines the identity of the element; for example, an atom with an atomic number of 6 is carbon, as it has six protons.

The atomic number also determines the chemical properties of the element and its place in the periodic table. Elements are organized in the periodic table by increasing atomic number, which reflects their proton count. This organization helps in understanding trends in element behavior and reactivity.

While neutrons and electrons contribute to an atom's mass and overall charge, they are not indicated by the atomic number. The total number of particles in the nucleus (which includes protons and neutrons) is given by the mass number, and the total mass of an atom takes into account the masses of protons, neutrons, and any electrons that may be present. Thus, the atomic number specifically highlights the number of protons in an element's nucleus, making it a key identifier for elements.