dChapter 4 - Subatomic Particles Atomic Models Physical...

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Subatomic Particles
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Atomic Models Physical model – a scale model of something either too big or small to study in its regular size Buildings Bacteria Conceptual model – a model used to describe a system, something that does not have a regular shape Atoms Weather
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The CDC often models infection routes when they study different infectious diseases and tries to track their origins. Which type of model would they be using? 1) physical 2) conceptual
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Subatomic Particles The electron was the first subatomic particle discovered Cathode ray tube – applying a voltage across a sealed tube of gas produces a particle beam (your parents’ TV)
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Since the particles were drawn toward the positive plate then they must have been negatively charged Thus electrons are noted as having a negative one (-1) charge
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Compared to the mass of a hydrogen atom electrons are very light, about 1/2000th of the weight of a hydrogen atom
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Atomic Model – J. J. Thompson The plum pudding model Answers these questions: Something must neutralize the negative charge of the electron How to combine both charges
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Atomic Model - Rutherford Ernest Rutherford Prove Plum-pudding Model Design: (1909) Using positively charged -particles (He nucleus) with high speed Using ultra-thin gold foil to avoid absorption Expected result -particles should pass through the gold foil virtually undisturbed
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Atomic Theory - Rutherford Experimental Results: Majority particles pass through without deflection Some particles deflected 1 in 20,000 bounced back Conclusion: Atoms must be mostly empty space with a massive, positively charged nucleus.
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Nuclear Components The nucleus: Protons (charge of +1) Neutrons (no charge) Also called nucleons Both protons and neutrons weigh about the same and are 2000x heavier than an electron (or approximately the weight of a hydrogen atom)
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Atomic Number This is the number of protons in an element and how we identify each element Hydrogen is the first element and has an atomic number of 1 Helium is the second element and has an atomic number of 2
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Mass number This is the number of nucleons in an atom Atoms of the same element always have the same atomic number but the mass
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Looking at subatomic particles in atoms
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Isotopes Isotopes are atoms of the same element that have different mass numbers If the identity of an element is determined by the number of protons what atomic particle must vary in an isotope?
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Isotope Practice How many neutrons are in U-238 (Atomic # of 92) 1) 92 2) 238 3) 146 4) 330
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This document was uploaded on 10/26/2011 for the course SPAN 1512 at South Plains College.

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dChapter 4 - Subatomic Particles Atomic Models Physical...

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