Learn how to distinguish between different isotopes of an element and understand the concept of relative atomic mass. This lesson covers atomic structure, isotopes, and calculations related to atomic weight. After this lesson, students will be able to: Define isotopes as atoms of the same element with different numbers of neutrons. Calculate the number of neutrons in an isotope given its mass number and atomic number with 100% accuracy in practice problems. Calculate the relative atomic mass of an element given the isotopic masses and their relative abundances with at least 80% accuracy.