First_Semester_Exam_Review - First Semester Exam...

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First Semester Exam Review (Have your periodic table out when studying this) Dalton’s Atomic Theory : Dolton was a scientist who based his early theories of atoms off of experimental data. The Theory: 1. All mater is composed of atoms 2. Atoms of a given element are the same in size mass and other properties 3. Atoms can not be created, destroyed, or subdivided (This was proven to be false, we can divide atoms into smaller units (atom bombs)) 4. Atoms can be combined separated or rearranged 5. The Law of Multiple Proportions- compounds form in whole number ratios Thomson’s Cathode Ray Tube Experiment: Proved the existence of electrons and that they had mass . The experiment: Dalton put a magnet around a cathode ray tube. When he turned it on, the Cathode ray (which is actually a bunch of electrons) bent towards the positive magnet. He also put a wheel inside of the ray tube and when the ray turned on he the wheel moved, proving that the charged particles in the ray had mass. By studying the curve of the ray and how many times the wheel turned, he found a mass to charge ratio for electrons (basically, he figured out how much charge was present in one gram of electrons). This experiment led to the Plum Pudding model of the atom. Rutherford’s Gold Foil Experiment: Proved the existence of a nucleus within the atom. Before this experiment scientists believed that atoms were homogeneous in composition, like a solid ball. What Rutherford did was he fired a beam of alpha particles (helium nucleuses) at gold foil. Most of the alpha particles continued through the foil but some of them were deflected in random directions. What this proved was that atoms were mostly empty space and that there was a small positive nucleus in the center. Now scientists used the nuclear atomic model of the atom (Jimmy Neutron) Isotopes : Atoms of the same element that have different number of neutrons Example: Different Isotopes of Sulfer: 32 33 16 S 16 S The top number is the mass number; the bottom number is the atomic number ***Note***: Atomic Mass is the decimal number on your periodic table. Mass Number is the number on the number of protons and neutrons. Radioactivity: All elements with an atomic number higher then lead are Radioactive. This is because there are so many protons and neutrons that the nucleus can’t be held together. All atoms want to be in the “band of stability” so they go under radioactive decay to achieve this.
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Radioactive Decay: There are three types of radioactive decay: Alpha, Beta, and Gamma Alpha: α, 2 4 He. A helium nucleus, has a charge of plus two, has a mass of 4 Beta: β, -1 0 e-, A high energy electron, charge of plus one, mass of
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This note was uploaded on 02/27/2012 for the course HIST 101 taught by Professor Wormer during the Spring '08 term at Benedictine IL.

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First_Semester_Exam_Review - First Semester Exam...

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