ISOTOPES. Atoms of the same element that contain different numbers of neutrons and have different atomic masses. If mass is not given, always add protons and neutrons. Examples: Carbon-13 13 6 C Oxygen-18 18 8 O. Average Atomic Mass.
If mass is not given, always add protons and neutrons.
AAM= x(mass of Isotope A)+(1-x)(mass of isotope B).
Solve for x and (1-x) to get the decimal fractional abundance…to get percent multiply them by 100.