Chemistry Chapter 5 & 6

Chemistry Chapter 5 & 6 - ChemistryChapter5&6...

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28/09/2008 13:15:00 HISTORY Democrits- (Greek) 400 BC hypothesized the existence of atom, as the smallest particle of matter DALTON (1800) John Dalton used experimental data to test a hypothesis= SCIENTIFIC THEORY o Daltons Atomic Theory 1. Each element is composed of atoms **2. Atoms of a given element are all the same. Atoms of different elements are different. (Not totally accurate) ** 3. Atoms are not changed into different atoms in a chemical reaction. (Not totally true) Compounds are formed when 2 or more elements combine 1 Proton= 3 quarks 1 Neutron = 1 quark Neutron- no charge *Proton- positive charge same mass as neutron Electron -negative charge, faraway from nuclei/ very small 1/2000 mass of proton Nucleus- center atom, most mass contained her very dense, protons and neutrons DISCOVERY ELECTON Thomas (1900) discovered the electron by using a cathode ray tube. **purposed that Cathode rays is ALWAYS composed of electrons( meant that electrons are the negative part of all elements) DISCOVERY of Mass of Electrons Milikan: used oil drop experiment to find mass of electron and it’s charge Discovery of Nucleus Rutherford (1920) showed that an atom has a VERY Small, Dense and POSTIVE nucleus. o GOLD foil EXPERIMENT
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used alpha particle= helium nucleus (2p 2n NO ELECTRONS) o DISCOVERED alpha particles (hit positive=repel) (hit something more dense) DISCOERY of NEUTRON Chadwick (1930) discovered the neutron by knowing the atomic mass
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Chemistry Chapter 5 & 6 - ChemistryChapter5&6...

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