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640 BCE
Democritus
A Greek philosopher who developed the concept of an 'atom' AKA 'invisible' in Greek for how extremely tiny it is. For his discovery, he took a seashell and broke it in half and he continued to break it in half over and over again until he was left with a powder. He took the smallest piece of the powder and tried to break it and couldn't. He they discovered atoms are like that powder, unbreakable and they're the main building blocks. -
John Dalton
John Dalton was an English chemist. His idea form the atomic theory of matter.He developed first useful atomic theory of matter . He concluded that evaporated water exists in the air as an independent ga. sHe performed a many experiments on mixtures of gases to determine what effect properties of the individual gases had on the properties of the mixtures as a whole. -
J.J. Thompson
He discovered electron when was experimenting with gas discharge tubes. He noticed a movement in the tube and called it "cathode rays".The rays moved from negative to positive because opposites attract. He later named the rays "electrons". -
Niels Bohr
He was a Danish physicist. He proposed a model of the atom that is similar to the model of the solar system. When the energy goes down, the level does too. This model is called the Bohr-Rutherford model because Bohr used many of Rutherford's ideas. -
Lord Ernest Rutherford
Conducted a famous experiment called the Gold Foil Experiment because he used a gold sheet of foil. Also used special equipment to shoot positively charged particles he called alpha particles at the gold foil.Claim that an atom was mostly empty space because most particles passed through the foil. He figured out that the nucleus was positively charged because the alpha particles repelled the nucleus and like charges repel. He was also responsible for the nuclear model of the atom.
