In this lesson our instructor talks about atoms, molecules, and ions. First, he discusses the atomic structure, isotopes, the periodic table, ionic compounds, and molecular compounds. Then he talks about the mole, percentage compositions, empirical and molecular formulas. He ends the lesson with a summary and two helpful sample problems. Atoms, Molecules, and Ions Rutherford’s gold foil experiment suggested the presence of the nucleus. Protons and neutrons reside inside the nucleus, while electrons are outside. Isotopes are atoms of the same element with different number of neutrons. The mole allows for conversion to/from number of units of anything. Dalton’s law of multiple proportions is demonstrated when solving for empirical and molecular formulas.