The atomic mass (A) of an element is calculated by adding what two components?

The atomic mass of an element is determined by the total number of protons and neutrons in the nucleus of an atom. Protons each have a mass of approximately one atomic mass unit (amu), and neutrons also have a mass close to one amu. Therefore, when adding the number of protons (which defines the element) and neutrons (which can vary in isotopes of the element), you obtain the atomic mass, typically expressed in atomic mass units.

While electrons contribute to the overall structure of the atom and its chemical behavior, they have very little mass compared to protons and neutrons (approximately 1/1836 of a proton's mass) and are not included in the calculation of atomic mass. Isotopes refer to variants of an element with the same number of protons but different numbers of neutrons, and while they pertain to the composition of atoms, they do not contribute as a separate component in the calculation of atomic mass. Thus, the correct method for finding atomic mass is to sum the number of protons and neutrons.