Ionic and Molecular Compounds

1
Ionic and Molecular Compounds

• Chapter 3

2
Classifying Compounds

• There are about 109 elements but they can be
  combined to make millions of compounds.
• Elements are commonly classified as METALS and
  NONMETALS, therefore compounds are formed three
  combinations

3

• metals-nonmetals ionic compounds
• NaCl
• nonmetal-nonmetal molecular compounds
• SO3
• metal-metal inter-molecular compounds
• Brass (CuZn) an alloy

4
Method for Classification

• The properties of compounds can be used to
  classify compounds as ionic or molecular
• Diagnostic Tests- a lab procedure conducted to
  identify or classify chemicals (appendix C, page
  595)
• Important states of matter in chemical formulas
  solid (s), liquid (l), gas (g), and aqueous (aq)

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Investigation 3.1Empirical Definitions of
Compounds

• Based on you experience, what properties might be
  used to classify compounds as ionic or molecular?
• Why is a control conductivity test on tap water?
• Disposal all chemical waste can be disposed
  down the drain with lots of water

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Evidence Table

• Chemical
• Formula
• Class (I or m)
• State (s, l, g)
• Solubility (yes/no)
• Solution color
• Electrical conductivity (yes/no)

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Evidence Table Inv. 3.1
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Analysis

• Empirical definitions what properties are true
  for ionic and molecular

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Evaluation

• What is judged to be adequate design, procedure,
  and skills?
• Are you confident in your results?
• Where your prediction correct?
• What can you do to improve your confidence in
  these definitions?

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Empirical or Theoretical Information?

• Both empirical and theoretical information is
  used to form the above definitions. Can you pick
  out what information is empirical on the previous
  slide?

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Definitions of Ionic and Molecular Compounds

• Ionic Compounds
• all solid at SATP
• aqueous solutions conduct electricity
• transfer of electrons when forming bonds
• metal-nonmetal
• Molecular Compounds
• solid, liquid and gases at SATP
• aqueous solutions do not conduct electricity
• share electrons when forming bonds
• nonmetal-nonmetal

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Lab Exercise 3A page 96

• In science, it is not uncommon for new evidence
  to conflict with widely known and accepted
  theories. This does not create a problem but an
  opportunity to improve understanding
• Lets test some more compounds and see if the
  properties turn out as we would predict

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Investigation 3.2 page 98

• Lets test some more compounds to support our
  empirical definitions for ionic and molecular
  compounds
• Evidence Table must include
• Chemical name
• Formula
• class
• State
• Electrical conductivity

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Evidence Table for Inv. 3.2
15

• Analysis
• Do the properties of the compounds match the
  predictions?
• Evaluation
• What is judged to be adequate design, procedure,
  and skills?
• Are you confident in your results?
• Where your predictions correct?
• What to do if something does not fitrestrict,
  revise or replace

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Restrict, Revise or Replace

• Problem hydrogen citrate (citric acid)
• C3H4OH(COOH)3
• This is made up of nonmetals so you would predict
  a molecular compound but it conducts electricity,
  and may be ionic.
• We need to a revision
• A third class of compounds called ACIDS

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Acids and Bases

• Acids
• are solid, liquid or gas as pure compounds at
  SATP
• aqueous solutions conduct electricity
• makes blue litmus paper turn red
• Bases
• contains hydroxide OH
• makes red litmus paper turn blue