Rarely the alpha particles struck the nuclei producing the extreme deflection. Define atomic number and mass number. Introduce the Nuclide symbol and determining the numbers of subatomic particles from it for neutral atoms and ions. Discuss isotopes giving examples. Define atomic mass distinguishing it from mass number.
Weighting factor is the natural abundance.
Determine the atomic mass of an element if given the natural abundance and masses of its isotopes. Determine the proportion of each isotope of an element when given the mass of each isotope and the atomic mass of the element. Discuss Mendeleev's Periodic Law and resulting table based on increasing atomic masses. Discuss Moseley's modern Periodic Law and resulting table based on increasing atomic numbers. The properties of the elements are a periodic function of their atomic numbers.