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(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 -
(384 BC) Aristotles atomic theory:
- Atoms did not move through empty space
- Did not believe that atoms existed. -
Created elements from water. He was the first to use hydrogen sulfide as a reactant.
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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. -
The declaration of independence was signed.
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Created a list of 23 known elements.
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Amedeo hypothesized that molecules of gas at the same tempurature have the same mass. He also stated that gasses were compounds of multiple molecules.
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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.
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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.
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The US civil war begins.
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President abraham lincoln was assassinated.
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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.
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Found how to separate radium from radioactive residues. She also isolated polonium.
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Albert einstein discovered the law of the photoelectric effect. which is finding how much energy was needed to eject electrons from a metals surface.
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Robert Millikan found the charge of an electron. When he found the charge, he was able to find the mass of a single electron.
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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.
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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.
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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.
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He discovered that atoms of different elements have different positive charges. He found that the amount of protons identifies a particular element.
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World war one begins.
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Created the de Brolie equaition that solves for the wavelength of a particle by using its mass and velocity.
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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.
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Heisenberg created the Geisenberg uncertainty principle that states it is impossible to know the velocity and position of a particle at the same time.
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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.
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World war two begins.
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Japan attacks the US and causes us to enter WWII
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videoThe manhatta project begins. The manhattan project was the construction of atomic bombs by the US.
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The first Chevrolet corvette is manufactured.
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John F. Kennedy is assassinated.
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Video Apollo 11 lands on the moon
