Final answer:
The atomic number represents the number of protons in an atom, which also equals the number of electrons in a neutral atom. It is a fundamental identifier for elements and is not related to the number of neutrons, which can vary among isotopes of the same element.
Step-by-step explanation:
The atomic number of an element represents the number of protons in the nucleus of an atom. This is a crucial identifier since it determines the element's identity. For example, the element carbon has an atomic number of 6, indicating the presence of six protons, regardless of the number of neutrons or electrons.
It is important to note that in a neutral atom, the number of protons is equal to the number of electrons. Hence, the atomic number also reveals the number of electrons in the atom. Unlike protons, the number of neutrons is not fixed and can vary among isotopes of the same element, which have the same atomic number but different mass numbers.
The total number of protons and neutrons, or nucleons, is known as the mass number (A). Therefore, you can calculate the number of neutrons by subtracting the atomic number from the mass number: A - Z = Number of Neutrons.