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Dalton Model
John Dalton came up with the theory of matter. He pictures atoms as tiny, indestructible particles, with no internal structure. There were four parts to his theory. (1) Matter is made up of atoms.
(2) Atoms can't be divided into smaller pieces
(3) All the atoms of an element are exactly alike
(4) Different elements are made of different atoms -
William Crookes' experiment
William Crookes did experiments with glass tubes and two electrodes sealed inside the tube. The electrodes were attached to a battery with wires. When he tested the experiment, he found that there was a green glow. Crookes hypothesized that "The green glow in the tube was caused by rays, or streams of particles." -
Thomson Model
J.J. Thompson placed a magnet next to Crookes tube to see if the beam bends. During the experiment the beam bended towards the magnet. Light can't bend so therefore the beam isn't light. Later he redid the CRT experiment Crookes did, but changing the metals and gasses to see if there was a difference. Thompson then concluded that negatively charged particles are called electrons. -
Hantaro Nagaoka
A japanese physicist, suggests that an atom has a central nucleus. Electrons move in orbits like the rings around the Saturn. -
Thompson upgrades model
During 1904 was when Thomson made his atomic model. The way he created his model was by modifying Dalton's model. Dalton's model was a sphere and looked like a marble. Thomson kept the shape a sphere but the sphere was the positively charged. He added scattered negatively charged electrons through out the sphere. -
Ernest Rutherford's experiment
In 1906, Ernest Rutherford wanted to find out if Thomson's model of the atom was correct. He tested this by doing the gold foil experiment. He set up the experiment by putting a piece of gold foil in the middle of a florescent screen. Every time a particle hit the screen, the screen would light up. Rutherford for was sure he new what the result would be, so he let a graduate try the experiment. Rutherford ended up being wrong because some of the particles bounced back instead of going straight t -
Rutherford Model
Rutherford made a new model of the atom. This atom shows a nucleus surrounded with lines going around it, and electrons going on top of the lines. He hypothesized that the positive charge in the atom is crammed into the center, known as the nucleus. -
Bohr Model
Niels Bohr calculated the energy levels the orbits would represent for the hydrogen atom. His calculations explained other scientists experimental data. Scientists soon learned that electrons move constantly in a unpredictable motion that can't be shown in a orbit. They determined that it was impossible to know the exact location of an electron. -
Rutherford upgrades
Rutherford figured out that the positive charges in the nucleus are protons. Protons are positively charged particles in the nucleus. Most of the alpha particles with little or no interference is because there is empty space that takes up most of the atom. But if the alpha particles made a direct hit to the gold foil, it would strongly bounce back. Many scientists were impressed with Rutherford's experiments. After many more questions, they found out about the neutron. A neutron is a negatively -
Louis de Brogile
French physicist Louis de Brogile proposes that moving particles like electrons have some properties of waves. Within a few years, experimental evidence supports the idea. -
Electron Cloud Model
Erwin Schrodinger develops mathematical equations to describe the motion of electrons in atoms. His work leads to the electron cloud model. -
James Chadwick
An english physicist, James Chadwick, confirms the existence of neutrons, which have no charge. Atomic nuclei contain neutrons and positively charged protons.
