Isotopes and atomic mass – mass number, abundance and average atomic mass

ChemistryAtomic Structure & Periodic TableAges 15–16

Choose an element, then drag neutrons into or out of the nucleus to build its isotopes (Z ≤ 10) and see the mass number, stability and natural abundance of each isotope. The Mix Isotopes screen lets you drop atoms one by one into a test tube, work out the average atomic mass of your mixture and compare it with the naturally occurring mixture. Adapted from the "Isotopes and Atomic Mass" simulation by PhET Interactive Simulations, University of Colorado Boulder (CC BY 4.0); rewritten.

Lesson: Atomic structure – isotopes and relative atomic mass