Chemists called this particle flow “cathode rays,” and they were able to detect them by placing a material called phosphors in the tube.

Most of the air was removed from the tube, but when the voltage is applied, the remaining particles flowed from the cathode to the anode. To create a cathode ray tube, Thomson applied a voltage to one side of a sealed glass container with two electrodes. Thomson discovered that there was a particle smaller than an atom - the electron - through his work with cathode ray tubes. However, in 1897, the English physicist J. The work of Avogadro on the volumes of gases and Robert Brown on Brownian motion further supported this hypothesis. This theory was established by Dalton and the atomists who stated that matter was made up of small indivisible particles known as elements which varied in their nature. The plum pudding model was the first model to suggest that atoms were not the smallest unit of matter, and that they may be made up of both positive and negatively charged subatomic particles.įor a long time, atoms were thought to be the smallest unit of matter.

What did the plum pudding model suggest about atoms? Instead of a sea of positive charges surrounding negative charged particles, atoms are actually organized with positive and neutral particles at their core (the nucleus) surrounded by orbitals of electrons.ģ. While the plum pudding model was the first to suggest that atoms are made up of charged particles, the plum pudding model is not entirely correct. This work was later expanded upon by chemists throughout the 19th century and beyond to create the modern model of the atom, which arose after the rise and fall of many partial theories.ġ.

The modern atomic model started to take shape with the work of Lavoisier and Dalton who formulated the concept of elements as unique iterations of atoms which can be combined in multiple ways to create a variety of substances. In 1913 Thomson published an influential monograph urging chemists to use the mass spectrograph in their analyses.Refresher: The atomic model originated in the 5th century BC when Greek philosophers hypothesized that all matter was composed of indivisible particles. His nonmathematical atomic theory-unlike early quantum theory-could also be used to account for chemical bonding and molecular structure (see Gilbert Newton Lewis and Irving Langmuir). Of all the physicists associated with determining the structure of the atom, Thomson remained most closely aligned to the chemical community. He was a good lecturer, encouraged his students, and devoted considerable attention to the wider problems of science teaching at university and secondary levels. Even though he was clumsy with his hands, he had a genius for designing apparatus and diagnosing its problems. In 1884 he was named to the prestigious Cavendish Professorship of Experimental Physics at Cambridge, although he had personally done very little experimental work. He was then recommended to Trinity College, Cambridge, where he became a mathematical physicist. Instead young Thomson attended Owens College, Manchester, which had an excellent science faculty. His father intended him to be an engineer, which in those days required an apprenticeship, but his family could not raise the necessary fee. Ironically, Thomson-great scientist and physics mentor-became a physicist by default. From 'The Growth of Physical Science,' by Sir James Hopwood Jeans (Cambridge: Cambridge University Press, 1948) Early Life and Education

William thomson cathode ray experiment