How do isotopes of an element affect the atomic mass calculation of that element? A The atomic mass of an element is based on the number of protons and neutrons of the element and the different isotopes of that element have no affect on the calculation. B The relative abundance of the different isotopes are expressed in atomic mass units which are totaled to determine the atomic mass. C The relative abundance of each isotope is expressed as a percentage which is used to calculate the atomic mass. D The atomic mass of an element is an average of the atomic masses of each isotope.