CHM 2045 chapter2 - Robert Millikan (oil drop experiment)...

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Chapter 2: Atoms and Elements Three subatomic particles make up all atoms: electrically positive protons, electrically neutral neutrons, and electrically negative electrons. *Atoms have no net charge—they balance out, because the number of electrons outside the nucleus equals the number of protons within the nucleus. Madam Curie (Marie curie): responsible for discovering radioactivity (certain substances emit rays when they disintegrate. 3 rays: alpha, beta, and gamma. Alpha and gamma are negatively charged and A particles are heavier than B particles. Gamma rays have no detectable charge and behave like light rays. Joseph John Thomson (responsible for the cathode ray): and Plum Pudding Model
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Unformatted text preview: Robert Millikan (oil drop experiment) learned that the charge of an electron by realizing its charge is a whole number. Earnest Rutherford: deserves credit for the discovery of the proton. Gold foil experiment: atoms contained a small positive charge nucleus with most of the mass of an atom. Called the center with all of the mass the nucleus. Chadwick: discovered the neutral neutron 2.2 Atomic Number and Atomic Mass All atoms of the same element have the same number of protons (The number of protons in the nucleus is called the atomic number) The sum of the number of protons and neutrons is called the mass number...
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