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Planner & Brain Teaser •Take out your planner •Record your test score •Answer this brain teaser: I am what poor people have and what rich people need. I am what blind people see and what deaf people hear. I am what brave people fear and what kind people hate. And though hateful people have me, only the biggest fools really know me. What am I? Ch 5 Structure of Matter Bonding, Naming & Writing Formulas of Compounds Do You Remember? • The difference between a mixture & a compound? –Which one changes properties when made? • Why does it take more energy to separate a compound? –Where is energy stored? Laws of Chemical Combination 1. Law of Definite Proportions – a pure compound has the same elemental composition regardless of its source. Ex. Table salt (sodium chloride) is salt no matter where or how it was made. It’s always NaCl 2. Law of Multiple Proportions – elements can combine in different ways to form different substances. Ex. Combine C, H, O in different ways to get different compounds like C12H22O11 - Sugar C6H10O5 - Starch Chemical Formulas •The subscript tells how many atoms of element in front of it. •If outside parentheses, the subscript applies to all inside. •Number 1 isn’t used in formulas; it’s implied. Compounds – chemical combinations What atoms and how many of each are in the formulas below? • Mg(OH)2 – 1 magnesium, 2 oxygen, 2 hydrogen • CuSO4 • Pb(NO2)4 • CH4 • Al(NO3)3 Molecular VS Empirical Formulas A molecular formula shows the exact number of atoms of each element in the smallest unit of a substance An empirical formula shows the simplest whole-number ratio of the atoms in a substance molecular empirical H2O H2O C6H12O6 CH2O O3 O N2H4 NH2 Change Molecular to Empirical Reduce the subscripts to show lowest whole numbers possible. • C5H10 5 goes into 5 once; 5 goes into 10 twice CH2 • C6H8O6 • Hg2F2 • CO2 • N2O4 • C6H14 Molecular Mass – determine the mass of the entire molecule • CH4 = 1 C @ 12 amu + 4 H @ 1 amu = 16amu • H20 • NO2 • C3H8 • CH3OOH • HBr Classes of Compounds • Ionic Compound – Metal (+ ion) attracted to nonmetal (– ion) – Held together by opposite charges (ionic bonds) – Smallest: formula unit • Covalent Compound – Electrons are shared (covalent bonds) – Usually between 2 or more nonmetals – Smallest: molecule Ionic or Covalent? How can you tell? Look to see if the elements are metal & nonmetal (ionic) or just nonmetal (covalent). • BaCl2 – Barium is metal, Chlorine is nonmetal = Ionic • H2O – Hydrogen is nonmetal, Oxygen is nonmetal = covalent • CaO • Fe2(SO4)3 • CO2 • NH3 • Fr2S Molecular Models Metallic Bonding Metallic bonds occur in metals. A metal consists of positive ions surrounded by a “sea” of mobile electrons. Four Characteristics of a Metallic Bond. 1. Good conductors of heat & electricity 2. Strong 3. Malleable and Ductile 4. Luster Network Solids Which have more attraction between molecules: solids, liquids, or gases? Covalent Network Solid – covalently bonded atoms linked in one big network or one big macromolecule. Ionic Network Solid – + ion & - ions attracted to each other High melting & boiling points – stuck together Review N2 ( )