Scientist
Democritus
“MC
Hammer”
Dalton
Model
Greek Model
Date
420 BC
Discovered/Ideas
Documented the idea of existence
atoms
Model Description
solid sphere
Billiard Ball Model
1800
Solid sphere
Thomson
Plum Pudding Model
1897
Proposed atomic theory
Said that atoms make elements and
elements combine to make compounds
Discovered the electron
Rutherford
Nuclear model/
Planetary Model
1911
Bohr
Planetary Model
1913
Schrodinger
Electron Cloud
Model or Quantum
Mechanical Model
1924
Chadwick
Neutron Model
1932
Through the “gold foil experiment”
discovered that atoms have to be
made up of mostly empty space,
dense, positively charged region in
the center that had to be small
compared to the total size of the
atom.
proposed that the electrons orbit in
distinct orbits, but electrons could
jump between these orbitals by
either gaining energy (moving to
farther away electron shells), or by
losing energy (falling to electron
shells closer to the nucleus)
came to view the atom not as a
nucleus surrounded by electrons
moving in perfectly circular orbits,
but that as electrons moving in
waves around the nucleus. Instead
of perfectly circular orbits, the
electrons would be found in clouds of
space around the nucleus.
Discovered/proved the existence of
neutrons
a sphere filled with a positively charged fluid,
and negatively charged particles
a dense region in the center, orbited by
electrons like the rings around the planet Saturn
electrons orbited the nucleus in concentric
circles
electrons are found in clouds of space around the
nucleus
Positively charged protons and similarly sized
neutrally charged neutrons exist inside the
positively charged nucleus