02_-_Intro_to_Chemistry

02_-_Intro_to_Chemistry - 02IntroductiontoChemistry...

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02 – Introduction to Chemistry 1.4-1.5, 2.7-2.8, 3.1-3.3 1 02 - Introduction to Chemistry
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Dalton’s Atomic Theory An atom is a minute, indivisible particle that is the smallest unit of a chemical element. Atoms are neither created nor destroyed in chemical reactions. For a given element, atoms have the same properties For atoms of different elements, these properties vary Atoms combine in fixed proportions to form compounds 2 02 - Introduction to Chemistry
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Physical VS Chemical Change Physical Change The sample may go from a liquid, to a solid, or to a vapour, or to some combination thereof Chemical make-up unchanged Chemical Change or Reaction A change in composition occurs Atoms are added to or lost from the initial sample Law of Conservation of Mass: The total mass of substances present before a chemical reaction is the same as the total mass after the reaction. 3 02 - Introduction to Chemistry
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Compounds and Molecules A molecule is the smallest unit that has the same proportion of elements as the overall compound For example: a water molecule (H 2 O) is composed of two hydrogen atoms (H) and one oxygen atom (O) Table salt is sodium chloride: Formula NaCl (the ratio of sodium to chlorine is 1:1) but it is not possible to identify a molecule of sodium chloride Law of Constant Composition: All samples of a compound have the same proportion by mass of the constituent elements. 4 02 - Introduction to Chemistry
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Nature of an Atom 5 There are three subatomic particles: Protons Neutrons Electrons The nuclear model of an atom suggests that the atom consists of: A nucleus of positive protons and neutral neutrons Smaller, negatively charged electrons orbit the nucleus www.chem4kids.com/files/atom_structure.html 02 - Introduction to Chemistry
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Nature of an Atom 6 Usually denoted as: Element Name (E) Mass Number (A): number of protons plus neutrons Atomic Number (Z): number of protons Is defined by the element and is often omitted For example, 14 N for nitrogen See the Periodic Table Periodic table is an arrangement of all the elements
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This note was uploaded on 09/17/2011 for the course CHE 102 taught by Professor Simon during the Spring '08 term at Waterloo.

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02_-_Intro_to_Chemistry - 02IntroductiontoChemistry...

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