Transcript History of the Atom

The History of the
Atomic Model
In other words, the old guys who
came up with the atom.
Democritus
460 BC - 370 BC
A Greek philosopher
proposed that all
matter was composed
of indivisible hard
balls called atoms
(Greek for
uncuttable).
 Unfortunately he was
unpopular and
ignored.

John Dalton
1803
Billiard Ball Model :
viewed the atom as a
small solid sphere.
 But he got the ball
rolling again to study
the atom.

Joseph John Thomson
1897


Plumb Pudding Model:
Proposed that the atom
was a sphere of positive
energy with negative
particles imbedded
throughout.
He was awarded the
Nobel Prize in physics in
1906 for discovering the
electron.
Ernest Rutherford
1910

Solar System Model:
discovered that the
atom is mostly empty
space with a dense
positively charged
nucleus surrounded
by negative electrons.
How Did He Know
He beamed particles
through gold foil and
detected them as
flashes of light .
 Most of the alpha
particles went straight
through the foil, but
some were deflected
by the foil and hit a
spot on a screen
placed off to one side.

Neils Bohr
1913

Proposed that
electrons traveled in
circular orbits and
that only certain
orbits were allowed.
Erwin Schrodinger
1926

Electron Cloud Model:
Using math Erwin
found that an atom
consists of a dense
nucleus composed of
protons and neutrons
surrounded by
electrons that exist in
different clouds at the
various energy levels.