ATOM - Timeline

1803 - Dalton proposes his Atomic Theory, stating that all substances are made of atoms.

400 BC - Democritus proposes first idea about the atom

340 BC - Aristotle proposes his theory about the elements, stating that all things are composed of fire, earth, air, and water.

1897 - Thomson discovered that atoms are in fact divisible, and composed of smaller charged particles.

1909 - Millikan discovers that the almost massless electrons have an extremely negative charge, through his oil drop experiment.

1911 - Rutherford performs his gold foil experiment and is able to discover the postitvely charged nucleus of the atom.

1913 - Bohr proposed a new model of the atom, in which the electrons are traveling around the nucleus in orbitals.

1928 - Schrodinger argues against Bohr's model claiming electrons to be more accurately viewed in "clouds."

1924 - De Brogile proposes that atoms can travel in waves.

1932 - Chadwick is able to discover the neutron.