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101
Greeks Theory
The Greeks thought atoms that started out as a piece of mass that was cut in half again and again until it could'nt be cut anymore. The Greek word for atom is "Atomos", which means indivisible. -
Period: 101 to
Timespan
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John Dalton's Theory
John Dalton wrote the first table of atomic weights. The 4 basic ideas in his book were 1) matter is made up of atoms 2) Atoms cannot be divided into smaller pieces 3) All the atoms of an element are exactly alike 4) Different substance are made up of different atoms. John Dalton's proposal was that an atom was a sphere, the same throughout. -
William Crooke
In 1870 William Crooke invented the Cathode Ray Tube (CRT). It consisted of 2 pieces of metal called electrodes. The positive cable was connnected to the anode and the negative cable was connected to the cathode. It glowed in the vacuum. He put the shadow in the anode end of the tube. These rays were called cathode rays. -
J.J Thompson's Theory
J.J Thompson proved the existence of the electron and proton. He worked with the Cathode Ray Tube (CRT). Cathode is the negative charge, Annode is the positive charge. Thompson determined the mass of the electron by multiplying -1.602 x 10 (-19) power x the mass of an electron. The Plum Pudding model : The atom is a very small mass of positive matter with negativly charged electrons embedded in the positive substance. When he put a magnet up to the CRT tube it was either attracted or repelled. -
Ernest Rutherford's Theory
Ernest Rutherford started an experiment to see if Thompson’s model of the atom was correct. They wanted to see what happened when they shot positivly charged particles, called alpha particles, through gold or a thin sheet of metal. Alpha particles repel from other postivly charged particles. The foil was surounded by a flouresant screen that gave a flash of light each time it was hit by a charged particle. Rutherford saw that the particles bounced back adn therfore he found the nucleus! -
Neils Bohr's Theory
The electrons are in orbits, or energy levels around the nucleus. The firsts orbit can hold 2 e. The second 8e. The third 8e. The fourth 8/18 e. Electrons are in unpredictable motion. So they say it is an electron cloud. He was awarded the Nobel Prize in 1922.
