ATOMS MODELS TIMELINE

Arisotle

300

~Mid 300's B.C
Four "elements": earth, fire, air, water
Believed in reasoning instead of scientific experiments
Dismissed Democritus' atom idea as "worthless"

Democritus of Adbera

400

~400 B.C (5th century B.C)
atomos= indivisible
First to identify possibility of an atom
Smallest piece of matter

John Dalton

Oct 3, 1803

~1803, 1805, 1808
Father of modern atomic theory
5 parts to theory
Includes elements are composed of atoms
Also inlcudes element's atoms are identical in mass

Joseph John "JJ" Thomson

Oct 29, 1897

~
Discovered electron
Described nature of cathode rays
Plum pudding model of atom

Max Planck

Oct 29, 1900

~
Atoms can emit "quanta"
Einstein used this scientist's work to study photons

Niels Bohr

Oct 29, 1913

Also 1915 and 1918
Planetary model of Atom
Electrons travel in specified energy levels
Spectrum lines produced when electrons move

Robert Milikan

Oct 29, 1924

~
Measure charge of an electron
Oil drop experiment
Completed with Thomson

Erwin Schrodinger

Oct 29, 1926

Showed mathematically that waves can be used to describe electrons in atoms
Determined probabilty location of electrons in atoms

Werner Heisenberg

Oct 29, 1932

~
"Uncertainty Principle"
Impossible to determine the position and the momentum of a particle at the same time
"Cloud" madel aka quantum mechanical model

James Chadwick

Oct 29, 1932

~1803, 1805, 1808
Father of modern atomic theory
5 parts to theory
Includes elements are composed of atoms
Also inlcudes element's atoms are identical in mass

Louis de Broglie

Oct 29, 1952

~
Electrons have properties of both waves and particles
Groups of waves was named after him

Ernest Rutherford

Oct 29, 2013

~
Gold foil eperiment
Atom has small positive nucleus, remainder is empty space
Predicted existence of neutrons