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Democritus
(460 BC) Democritus created his own atomic theory which stated:
- Atoms move through empty space in matter
- Atoms are solid, indestructable and invisible
- Properties of matter are due to the arrangement, size, shape and movement of atoms, not from changes in the atoms themselves -
Aristotle
(384 BC) Aristotles atomic theory:
- Atoms did not move through empty space
- Did not believe that atoms existed. -
Joseph Proust
Created elements from water. He was the first to use hydrogen sulfide as a reactant. -
John Dalton
videoDalton's atomic theory:
- All matter is composed of atoms
- All atoms of the a given element are exactly the same
- Atoms cannot be created or destroyed.
- In a chemical reaction atoms are separated, combined, or rearranged. -
Signing of the declaration of independence
The declaration of independence was signed. -
Antoine Lavoisier
Created a list of 23 known elements. -
Amedeo Avogadro
Amedeo hypothesized that molecules of gas at the same tempurature have the same mass. He also stated that gasses were compounds of multiple molecules. -
William Crookes
VideoWas experimenting with vacuum tubes and noticed a flash of light. He found out that the light was caused by radiation striking a light producing coating. The radiation originated from the cathode end of the tube so it was called a cathode tube. This led to the invention of the television. -
J.J. Thomson
Experimented with cathode rays and tried to determine the ratio of its charge to its mass. He measured the effect of magnetic and electric fields on the cathode ray. He proved that atoms were divisible into smaller particles. -
Beginning of the Civil war
The US civil war begins. -
Lincoln's assassination
President abraham lincoln was assassinated. -
Henri Becquerel
videoBecquerel discovered spontanious radioactivity. He discovered that uranium salts gave off radiation that could be registered on a photographic plate. He was the first to discover radioactivity. -
Madame Curie
Found how to separate radium from radioactive residues. She also isolated polonium. -
Albert Einstein
Albert einstein discovered the law of the photoelectric effect. which is finding how much energy was needed to eject electrons from a metals surface. -
Robert Millikan
Robert Millikan found the charge of an electron. When he found the charge, he was able to find the mass of a single electron. -
Ernest Rutherford
Ernest Rutherford studied how positive alpha particles reacted with solid matter. He disproved the plum pudding model and found that electrons in an atom moved through empty space and also found that there was a dense region in the center that he called a nucleus. He also discovered that there are positively charged protons in a nucleus. -
James Chadwick
James Chadwick discovered that there was another subatomic particle in the nucleus of an atom called a neutron. He found that a neutron has no electrical charge. -
Niels Bohr
Bohr stated that hydrogen atoms have certain allowable energy states. The lowest is the cround state and when it gains energy it is in an excited state. He then related the energy states to the motion of the electron in the atom. He states that the smaller the orbit, the lower the energy level. -
Henry Moseley
He discovered that atoms of different elements have different positive charges. He found that the amount of protons identifies a particular element. -
World War One
World war one begins. -
Louis de Broglie
Created the de Brolie equaition that solves for the wavelength of a particle by using its mass and velocity. -
Max Planck
Believed to be the originator of the quantum theory that explains the behavior of atoms. He found that matter can gain or lose energy only in small amounts called quanta. -
Werner Heisenberg
Heisenberg created the Geisenberg uncertainty principle that states it is impossible to know the velocity and position of a particle at the same time. -
Erwin Schrodinger
Schrodinger found an equation that treated the atom's electron as a wave. This equation worked for other elements, where Bohr's equation did not. -
World war two begins
World war two begins. -
Pearl Harbor
Japan attacks the US and causes us to enter WWII -
The manhattan project
videoThe manhatta project begins. The manhattan project was the construction of atomic bombs by the US. -
First corvette
The first Chevrolet corvette is manufactured. -
JFK assassination
John F. Kennedy is assassinated. -
