This series uses demonstrations and animations to take students on a journey of discovery to explain what we know about atoms -- and how we know what we know about atoms. The Fifth episode examines the experiments that lead to the discovery of protons, neutrons, and electrons. By explaining the basics of atoms, students can better understand the chemical reactions which led to their discovery.

Originally released by Liacos Educational Media, 2015. Streaming video file encoded with permission for digital streaming by Infobase on September 26, 2015. Link to website with Teacher's notes and Question Sheet for students available under Additional info tag.

Protons, Neutrons, and Electrons --(1:53) -- Atomic Structure -- (4:42) -- Atomic Structure, Part 2 -- (6:19) -- Discovery of Electrons -- (4:54) -- Alpha Particles -- (7:35) -- Rutherford's Gold Foil Experiments -- (3:59) -- Discovery of Protons and Neutrons -- (5:22) -- Discovery of Protons and Neutrons, Part 2 -- (3:49) -- Credits: Protons, Neutrons, and Electrons: Shedding Light on Atoms, Episode 5 -- (0:18). Part A: Introduction: We look back briefly at how the Periodic Table was developed and introduce the fact that atoms are made of three types of particles called protons, neutrons and electrons. Part B: Atomic Structure: We show that atoms are made of a central nucleus (which is composed of positively charged protons and neutral neutrons), which is surrounded by negatively charged electrons. We explain that it is the number of protons in an atom’s nucleus which uniquely defines each atom. We also take a look at what isotopes are. Part C: The Discovery of Electrons: In the late 1890s, J.J. Thomson discovered electrons. We explain how he did this by demonstrating some of the equipment he used in his lab. We also take a close look at static electricity. Part D: Alpha Particles: The discovery of radioactivity in the 1890s opened up a new window into the study of atoms and their structure. Part E: Rutherford’s Gold-Foil Experiment: In 1908, Ernest Rutherford used high-speed alpha particles (produced by radioactive radium) to probe into the structure of the atom and his experimental results changed our whole idea of what atoms were like. He discovered that atoms had a positively charged nucleus which was surrounded by orbiting electrons. Part F: The Discovery of Protons and Neutrons: We take a look at how, after the discovery of the nucleus, protons and neutrons were discovered. .