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460 BCE
Democritus
Democritus was a Greek philosopher who discovered an atom that was made of tiny, indivisible, and indestructible particles. Unfortunately, his ideas were rejected because he didn't have the necessary equipment. https://www.youtube.com/watch?v=TgWn91ap99A -
J. J Thompson
J. J Thompson was an English scientist that discovered the electron when he was experimenting with gas discharge tubes. He then noticed movement in the tube and he called it cathode rays, which moved from the negative end of the tube to the positive end. Thompson realized that he discovered electrons that were negatively charged particles. https://www.youtube.com/watch?v=RW_zfKOU9uM -
Lord Ernest Rutherford
Ernest Rutherford conducted a famous experiment called the gold foil experiment. It was called this because he used a thin sheet of gold foil, and during his experiment he would shoot alpha particles at the gold foil. When this happened the alpha particles went straight back or deflected. Also alpha particles are positively charged. Lastly the experiment shows that atoms are mostly empty space, and they are made from a small positive nucleus. https://www.youtube.com/watch?v=Xb9KnwadI6Y -
Niels Bohr
Niels Bohr was a Danish physicist, who had a model called a planetary model of the atom. It was called this because the electrons go around the nucleus like planets orbit around the sun. Also, in Bohr's model each energy level had its own amount of electrons. For example, the fourth energy level holds 32 electrons. Another thing is when electrons release energy they go down a level, and when they gain energy they go to a higher level. https://www.youtube.com/watch?v=Cn6v5ygyZHQ
