CK-12 Foundation
Ck 12: Structure of the Atom
[Free Registration/Login may be required to access all resource tools.] Students learn about the important discoveries of subatomic particles, and how they led to our current understanding of the atom.
PBS
Pbs: Planck Discovers the Quantum Nature of Energy
PBS offers a short summary of the discovery of the quantum nature of the atom by Max Planck. Easy to follow.
National High Magnetic Field Laboratory
Magnet Academy: Timeline of Electricity and Magnetism: 1910 1929
Scientists' understanding of the structure of the atom and of its component particles grows, the phone and radio become common, and the modern television is born.