What determines the atomic number of an atom?

The atomic number of an atom is determined by the number of protons it contains. Each element on the periodic table is defined by its atomic number, which uniquely identifies the element. For example, an atom with one proton is hydrogen, while an atom with six protons is carbon. The atomic number is crucial because it not only identifies the element but also influences the chemical properties and behaviors of that element.

While the number of neutrons can vary in different isotopes of the same element, and the number of electrons can change in ions, it is the number of protons that dictates the atomic number and thereby the identity of the element itself. Hence, this number remains consistent across all atoms of a given element, regardless of potential variations in neutrons or electrons.