J.J. Thomson Atomic Theory and Biography

Sir Joseph John Thomson, physicist and inventor, 1900.
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Sir Joseph John Thomson or J.J. Thomson is best known as the man who discovered the electron.

J.J. Thomson Biographical Data

Tomson was born December 18, 1856, Cheetham Hill, near Manchester, England. He died August 30, 1940, Cambridge, Cambridgeshire, England. Thomson is buried in Westminster Abbey, near Sir Isaac Newton. J.J. Thomson is credited with the discovery of the electron, the negatively charged particle in the atom. He is known for the Thomson atomic theory.

Many scientists studied the electric discharge of a cathode ray tube. It was Thomson's interpretation that was important. He took the deflection of the rays by the magnets and charged plates as evidence of "bodies much smaller than atoms." Thomson calculated these bodies had a large charge-to-mass ratio and he estimated the value of the charge itself. In 1904, Thomson proposed a model of the atom as a sphere of positive matter with electrons positioned based on electrostatic forces. So, he not only discovered the electron but determined it was a fundamental part of an atom.

Notable awards Thomson received include:

  • Nobel Prize in Physics (1906) "in recognition of the great merits of his theoretical and experimental investigations on the conduction of electricity by gases" 
  • Knighted (1908)
  • Cavendish Professor of Experimental Physics at Cambridge (1884–1918)

Thomson Atomic Theory

Thomson's discovery of the electron completely changed the way people viewed atoms. Up until the end of the 19th century, atoms were thought to be tiny solid spheres. In 1903, Thomson proposed a model of the atom consisting of positive and negative charges, present in equal amounts so that an atom would be electrically neutral. He proposed the atom was a sphere, but the positive and negative charges were embedded within it. Thomson's model came to be called the "plum pudding model" or "chocolate chip cookie model". Modern scientists understand atoms consist of a nucleus of positively-charged protons and neutral neutrons, with negatively-charged electrons orbiting the nucleus. Yet, Thomson's model is important because it introduced the notion that an atom consisted of charged particles.

Interesting Facts About J.J. Thomson

  • Prior to Thomson's discovery of electrons, scientists believed the atom was the smallest fundamental unit of matter.
  • Thomson called the particle he discovered 'corpuscles' rather than electrons.
  • Thomson's master's work, Treatise on the motion of vortex rings, provides a mathematical description of William Thomson's vortex theory of atoms. He was awarded the Adams Prize in 1884.
  • Thomson discovered the natural radioactivity of potassium in 1905.
  • In 1906, Thomson demonstrated a hydrogen atom had only a single electron.
  • Thomson's father intended for J.J. to be an engineer, but the family did not have the funds to support the apprenticeship. So, Joseph John attended Owens College in Manchester, and then Trinity College in Cambridge, where he became a mathematical physicist. 
  • In 1890, Thomson married one of his students, Rose Elisabeth Paget. They had a son and a daughter. The son, Sir George Paget Thomson, received the Nobel Prize in Physics in 1937.
  • Thomson also investigated the nature of positively-charged particles. These experiments led to the development of the mass spectrograph.
  • Thomson was closely aligned with chemists of the time. His atomic theory helped explain atomic bonding and the structure of molecules. Thomson published an important monograph in 1913 urging the use of the mass spectrograph in chemical analysis.
  • Many consider J.J. Thomson's greatest contribution to science to be his role as a teacher. Seven of his research assistants, as well as his own son, went on to win the Nobel Prize in Physics. One of his best-known students was Ernest Rutherford, who succeeded Thomson as Cavendish Professor of Physics.
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Helmenstine, Anne Marie, Ph.D. "J.J. Thomson Atomic Theory and Biography." ThoughtCo, Apr. 5, 2023, thoughtco.com/j-j-thomson-biography-607780. Helmenstine, Anne Marie, Ph.D. (2023, April 5). J.J. Thomson Atomic Theory and Biography. Retrieved from https://www.thoughtco.com/j-j-thomson-biography-607780 Helmenstine, Anne Marie, Ph.D. "J.J. Thomson Atomic Theory and Biography." ThoughtCo. https://www.thoughtco.com/j-j-thomson-biography-607780 (accessed May 29, 2023).