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.
Other
Iun: Modern Atomic Theory
This is an excellent site with information on the discovery of the atom and the different models. Includes a sample question and answer using Planck's constant.
Concord Consortium
The Concord Consortium: Molecular Workbench Zoom It
See examples of scales based on a range from ten to the twelfth meters to ten to the negative twelth meters. Examples range from parts of our solar system to the nucleus of an atom.
CK-12 Foundation
Ck 12: Evolution of the Atomic Model
[Free Registration/Login may be required to access all resource tools.] Students take a closer look at how our understanding of the atom has evolved over time.
Science Struck
Science Struck: The Structure of an Atom: A Labeled Diagram
Looks at the scientists who developed the model of the atom by building on previous scientists' discoveries about its structure.
PBS
Pbs: Chadwick and the Neutron
PBS provides a brief overview regarding Chadwick's discovery of the neutron.