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?

Bonding, Naming & Writing Formulas of Compounds 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 - C6H10O5 - Sugar 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 Mg(OH)2 – 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 H2O molecular empirical 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 Covalent 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. Good conductors of heat & electricity Strong Malleable and Ductile Luster

High melting & boiling points – stuck together 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

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