Discovery of the
Electron, Models &
Theories
Jeffrey
Thorin
Daniel
JJ Thompson Robert Millikan
• Discovered the electron
• Wrote books on atomic
theory and structure
• First to suggest that
atoms have parts
• Found the accurate way
to decide the charge
carried with an atom
Niels Bohr
• Helped create a picture
of the atomic
structure(Bohr model)
• This said that electrons
orbit the nucleus in
fixed circular orbits
Louis de Broglie
• Looked into Bohr’s
investigation and
thought electrons
moved in waves rather
that circular orbits
Werner Heisenberg
• Known for his theory in
quantum mechanics
• Proved Bohr’s theory
wrong about the
movement of electrons
• Said we can’t assign to
an electron a position in
space at a given time,
nor follow it in its orbit
Erwin Schrodinger
• Developed a waveequation that
accurately gave
energy levels to
atoms
Bohr Model

An atom consisting of small positively charged nucleus orbited by negatively
charged electrons

Similar to planetary model where planets orbit the Sun

Solar system uses gravitational forces whereas an atom uses electrostatic forces

Electrons have certain orbits with certain radii

Orbits are circular according to quantized energy levels

Orbits with larger radii have larger energies
Quantum Model
 Based on quantum theory, which says matter also has
properties associated with waves
 Impossible to know the exact position and momentum
of an electron at the same time
 Uses complex shapes of orbitals (electron clouds)
volumes of space in which there is likely to be an
electron
 Based on probability rather than certainty
Experiments
 Thompson experimented with cathode rays and magnets that led to the
discovery of the electron
 Millikan devised an oil-drop experiment where he’d drop tiny charged
droplets to find out their specific charge
 Bohr based his model on experiments done by Ernest Rutherford; he saw
Rutherford’s model wasn’t quite right and changed it
 Broglie saw that Bohr’s model, specifically the electrons, move in waves,
not in a circular orbit
 Heisenberg also went off of Bohr’s model and elaborated more into
quantum mechanics to explain the wave motion of electrons instead of a
circular orbit
 Schrodinger used mathematical equations to predict the likelihood of
finding the electron and eventually found one that worked
Time Line of History
 Scientists from the early 1900s
 Theories developed without use of more precise
modern technology
Over time…
 Bohr’s model had a lot of problems and inaccuracies
to it
 Quantum model is considered “standard” and is also
considered the most accurate physical theory ever
created