BY , KY L E G RA H N & R I L E Y H A N N A N

J.J. THOMSON AND THE ELECTRON

BIOGRAPHICAL SKETCH

• Born- December 18, 1856 in Cheetham Hill, Manchester, United Kingdom• Died- August 30, 1940 in Cambridge, England,

UK• He was 83 years old• Attended and did most significant work at

University of Cambridge • Competed with William Prout and Norman Lockyer • Inspired by discovery of the X-RAY in 1895

MOST IMPORTANT WORK

• Discovered the electron

• In 1897 J. J. Thomson discovered the electron in a series of experiments designed to study the nature of electric discharge in a high-vacuum cathode-ray tube, an area being investigated by numerous scientists at the time.

• J.J. Thomson's discovery of the electron in 1897 showed us that the atom can be split into even smaller parts. His discovery was the first step towards a detailed model of the atom.

DISCOVERY OF THE ELECTRON

• JJ was very curious why and how the cathode ray tube worked• He placed cathode tubes in electric and magnetic

fields. He knew that these fields will move particles from side to side, but don't have much effect on how a wave moves.• In his experiments, the cathode rays bent over to

one side, so Thomson knew the cathode rays must be made of some small particle, which he dubbed a "corpuscle."

DISCOVERY OF THE ELECTRON

• Thomson initially thought his corpuscles were much too small to be of interest to anyone outside a science lab. However, people quickly realized that electric current was in fact made of moving electrons.• Since electricity is the lifeblood of everything

from computers to phones to microwaves, the electron turned out to be interesting to just about everybody. 

DEVELOPMENT IN ATOMIC THEORY

• J.J. Thomson measured e/m ratio by using a cathode ray tube and applying electrical and magnetic fields perpendicular to each other as well as to the path of electrons.

• E= the electrical field• M= Mass of particle

Diagram of cathode ray tube

DISCOVERY OF THE ISOTOPE OF NEON

• Neon played a role in the basic understanding of the atoms in 1913, when J. J. Thomson, as part of his exploration into the composition of canal rays, channeled streams of neon ions through a magnetic and an electric field and measured their deflection by placing a photographic plate in their path.• Thomson observed two separate patches of light

on the photographic plate, which suggested two different parabolas of deflection.

DISCOVERY OF THE ISOTOPE OF NEON

• Thomson eventually concluded that some of the atoms in the neon gas were of higher mass than the rest. • Though not understood at the time by Thomson,

this was the first discovery of isotopes of stable atoms.• It was made by using a crude version of an

instrument we now term as a mass spectrometer.

PLUM PUDDING MODEL

• Thomson proposed that the bulk of an atom consisted of a positively charged substance with electrons embedded in it.• The inside of the watermelon is the positively

charged where the electrons are. The watermelon interior is red, corresponding to the positive charge. The black seeds represent the electrons which are embedded in the atom in circles just as Thomson suggested.

IMAGE THIS AS A WATERMELON

Do you see the similarity?

WORK CITED

• http://www.chemheritage.org/discover/online-resources/chemistry-in-history/themes/atomic-and-nuclear-structure/thomson.aspx• The Basics of Electronics (Hardcover)• We found this in the library • http://www.pbs.org/transistor/science/events/

electron.html