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1.) All elements are composed of atoms
2.)Atoms of the same element are identical
3.0Atoms of different elements combine in simple whole-number ratios to form chemical compounds. -
Gases that first became possible at the turn of the nineteenth century led John Dalton in 1803 to propose a modern theory of the atom based on the following assumptions. 1. Matter is made up of atoms that are indivisible and indestructible.
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He was an early investigator of discharge tubes, the discoverer of anode rays, and is credited with the discovery of the proton.
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He created the Plum pudding model
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Robert Millikan was a physicist who discovered the elementary charge of an electron using the oil-drop experiment.
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The nuclear structure of the atom discovered alpha and beta rays and proposed the laws of radioactive decay
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It is a system consisting of a small, dense nucleus surrounded by orbiting electrons—similar to the structure of the Solar System, but with attraction provided by electrostatic forces in place of gravity.
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Bombarded beryllium atoms with alpha particles. Unknown radiation was produced. Chadwick interpreted this radiation as being composed of particles with a neutral electrical charge and the approximate mass of a proton.
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It is the ninth transuranium element of the actinide series discovered. It was first identified by Ghiorso, Harvey, Choppin, Thompson, and Seaborg in early in 1955 during the bombardment