|Event Date:||Event Title:||Event Description:|
|Aristotle ~ 300 BC||Mid 300's BC (After Democritus)|
|Aristotle ~300 BC||Mid 300's BC (After Democritus)|
|Democritus of Adbera ~400 BC|
|John Dalton||1.All matter is composed of called atoms.
2.All atoms of a given element are identical.
3.Atoms cannot be created, destroyed, or subdivided.
4.In chemical reactions, atoms combine with or separate from other atoms.
5.In chemical reactions, atoms combine with each other in simple, whole-number ratios to form combined atoms
|Joseph John (J.J.) Thomson||discovers the electron described the nature of cathode rays plum pudding model of the atom|
|Ernest Rutherford||Rutherford discovered alpha, beta, and gamma rays in radiation.|
|Max Planck||Max Planck proposed the idea of quantization to explain how a hot, glowing object emitted light.
determined atoms can emit "quants"
Einstein used his work to study photons
|Ernest Rutherford||Conducted the gold foil experiment: Rutherford fired tiny alpha particles at solid objects such as gold foil. He found that while most of the alpha particles passed right through the gold foil, a small number of alpha particles passed through at an angle (as if they had bumped up against something) and some bounced straight back like a tennis ball hitting a wall. Rutherford's experiments suggested that gold foil, and matter in general, had holes in it!|
|Neils Bohr||discovers electrons travel in specified energy levels; and spectrum lines are produced when electrons move.
He comes up with his planetary model of the atom
|Ernest Rutherford||Determined the atom has a small nucleus, and the remainder is empty space|
|Ernest Rutherford||predicted the existence of neutrons|
|Neils Bohr||Niels Bohr proposed an atomic structure theory that stated the outer orbit of an atom could hold more electrons than the inner orbit.|
|Louis de Broglie||added to Bohr's model of the atom by reasoning that, since light could act like a particle, an electron could act like a wave.
Determined that electrons have properties of both waves and particles
this group of waves is named after this scientist
|Werner Heisenberg||*Quantum mechanics describes the time evolution of physical systems via the wave function
*The wave function encapsulates the probability that the system is to be found in a given state at a given time
|James Chadwick||discovered neutrons, particles whose mass was close to that of a proton. helped with the development of the nuclear model|