http://www.ck12.org Chapter 2. Matter
particles together?” The quest for fundamental particles began thousands of years ago. Scientists thought they had
finally found them when John Dalton discovered the atom in 1803 (see the timeline inTable2.7). The word atom
means “indivisible,” and Dalton thought that the atom could not be divided into smaller, simpler particles.
TABLE2.7: Timeline of Discovery of Fundamental Particles
Year Discovery
1803 John Dalton discovers the atom.1897 J.J. Thomson discovers the electron, the first lepton to
be discovered.1905 Albert Einstein discovers the photon, the first boson to
be discovered.