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Benjamin Franklin
He discovered that electrical charges come in 2 varieties – positive and negative. Like charges repel, opposite charges attract. -
William Crookes
He came up with the CRT (Cathode Ray Tube). A CRT is a glass tube that is evacuated (contains no air or matter) coated with fluorescent paint. When connected to a battery, the paint glows, indicating that there is some type of radiation streaming from the battery (the cathode). When he placed a paddle wheel in the CRT and turned on the battery, the wheel spun. Since the tube was evacuated, it told him that the Cathode Ray has mass. He made the discovery of thallium. -
Sir John Joseph Thomson
He continued experimenting on the CRT and used charged plates to deflect the cathode ray. He discovered that the ray deflected away from the negative plates and went towards the positive. He deduced that the cathode ray was made of negative particles which he named them electrons. He theorized the electromagnetic mass of a charged particle and demonstrated that speed increased the mass of a charged particle. He found out that cathode rays were 1000 times lighter than the hydrogen atom. -
Ernest Rutherford part 1
He classified radiation. In 1910 he did the famous gold foil experiment. He stretched a sheet of gold foil in a tin can and coated the inside of the can with fluorescent paint. Then he aimed a ray of alpha radiation (+ charges) at the foil. Expected that the alpha rays would pass right through the metal atoms in the foil, and the fluorescent coating would light up right behind the foil. -
Ernest Rutherford part 2
He observed that 99.9% of the time, the ray lit up the can right behind the foil,but .1% of the time, the ray lit up the can OPPOSITE the foil. (behind the alpha source). This told him that the ray had hit something massive and dense in the center of the atom. He deduced that atoms are mostly empty space.There must be a solid core in the center of the atom.The core must be positively charged, since it deflected an alpha ray. -
Becquerel
He discovered radioactivity in Uranium ore. His doctoral thesis was on the plane polarization of light and the phosphorescence and absorption of light by crystals. He was studying the effects of light on uranium salts which he discovered that uranium spontaneously emits a type of radiation. -
Curies (Marie and Pierre)
They discovered and isolated polonium and radium from uranium ores. Together, they found that two ores, chalcolite and pitchblende, were much more radioactive than pure uranium. The Curies found that two of the chemical components, one containing mostly bismuth and another containing mostly barium, were strongly radioactive. -
Millikan
He calculated the mass and charge of an electron. Millikan proved that radiation is from an extraterrestrial origin, and named it “cosmic rays. Robert began experimenting with electrical charges, and electrons. His experiment became known as the Millikan oil-drop experiment. -
James Chadwick
He proved the existence of another subatomic particle, that had no charge and named it the neutron. His research with radioactivity had for years pointed to the presence of a light particle with no electrical charge in the nucleus of atoms. His discovery made it possible to artificially create elements heavier than uranium.
