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400 BCE
Democritus
Democritus was a Greek philosopher who proposed the idea that matter is made of tiny, indivisible, indestructible particles the he called, "atomos", from which the English word atom (meaning cannot be separated) was made. He did not have the correct equipment to test his notion by using controlled experiments. and his ideas were subsequently rejected. Facts:
He promulgated the atomic theory.
He was born in Abdera
https://www.youtube.com/watch?v=fEdAvTMYNRU -
John Dalton
John Dalton was an English chemist. His notions from the atomic theory of matter. some of his ideas were that atoms were indestructible, all atoms of the same element are alike, atoms of different elements are different, and atoms of a different element combine to form a compound. Facts:
Was born September 6, 1766, in Eaglesfield, England.
He went on to be named a mathematics and philosophy teacher at the New College in Manchester. -
J.J. Thompson
J.J. was an English scientist. He discovered the electron when he was experimenting with gas discharge tubes. He noticed a movement in a tube. He called the movement cathode rays. The rays moved from the negative end of the tube to the positive end of the tube. He realized that the rays were made of negatively charged particles - electrons. -
Lord Ernest Rutherford
Lord Ernest conducted a well-known experiment called the gold foil experiment. He used special equipment to shoot alpha particles at the gold foil. Most particles passed straight through the foil like the foil was not there. Some alpha particles went straight back or were deflected (went in another direction) as if they hit something. He learned that atoms are made of a small positive nucleus; positive nucleus repels and atoms are mostly empty space. https://www.youtube.com/watch?v=XBqHkraf8iE -
Niels Bohr
Niels Bohr was a Danish physicist. He proposed a model of the atom that is similar to the model of the solar system. The electrons go around the nucleus like planet orbit around the sun. All electrons have their energy levels - a certain distance from the nucleus. Each energy level can hold a certain number of electrons. Level one can hold 2 electrons, Level 2 - 8 electrons, Level 3 - 18 electrons, and Level 4 - 32 electrons.
https://www.youtube.com/watch?v=GhAn8xZQ-d8
