J.J. THOMSON AND
THE ELECTRON
BY, KYLE GRAHN & RILEY HANNAN
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.
Diagram of cathode ray tube
• E= the electrical field
• M= Mass of particle
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/onlineresources/chemistry-in-history/themes/atomic-andnuclear-structure/thomson.aspx
• The Basics of Electronics (Hardcover)
• We found this in the library
• http://www.pbs.org/transistor/science/events/elect
ron.html