The Electron

Until the very late 1800s, the atom was believed to be the very smallest particle that was involved in chemical reactions. In 1897, the British physicist J.J. Thomson discovered a negatively-charged particle called the electron. By experimenting with a magnet, Thomson figured out that the atom must have small particles in it with a negative charge. In this topic, you will explore the history of the discovery of the electron.

Essential Question

• How was the electron discovered?