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Chapter 3 Topics Chapter 3 1. Ionic and Molecular Compounds 2. Monatomic and Polyatomic Chemical 3. Formulas for Ionic Compounds Compounds 4. Naming Ionic Compounds 5. Naming and Writing Formulas for Molecular Compounds 6. and Bases 7. Predicting Properties and Naming Compounds

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Water is part of the earth, ocean, rivers, How does conduct electricity? and atmosphere. • Water conducts electricity because it contains ions. When compounds containing ions dissolve in water, the ions exist separate from each other. The mobility of ions allows for a current to pass through water.

Figure 3.02 3 4 3 Figure 3.03 4

Electrolytes Compound Names and Classifications

• containing • CH3CO2H – acetic , acid ions are . • HCl – , acid

• HNO3 – nitric acid, acid • • NaCl – , ionic compound dissolved in water is an dissolved in water is an • CH OH – methanol, molecular compound . 3

Dissolve

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1 Ionic and Molecular Compounds

• An ionic compound consists of oppositely • NaCl is an ionic charged cations and anions. Usually the compound cation is a metal and the anion is a nonmetal or a group of nonmetals. (ie, NaCl) • CO2 is a molecular compound • A molecular compound consists of two or compound more different nonmetals. It exists as a O is a molecular discrete unit of . (ie, CO ) • O2 is a molecular 2 element Figure 3.07

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Identifying Ionic and Molecular Identifying Ionic and Molecular Compounds Compounds

Identify each compound as ionic or molecular. Identify each compound as ionic or molecular.

• CCl4 • CCl4 • CaF2 classify • CaF2 • SF6 • SF6 • CuCO3 • CuCO 3 • H2O • H2O

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When an ionic compound dissolves in Most molecular substances do not water, it dissociates into its ions. dissociate in water.

• Most molecular NaCl(s) Æ Na+(aq) + Cl−(aq) • substances, such as

CH3OH or O2, do not dissociate into ions in aqueous . The remain intact.

• CH3OH(l) Æ CH3OH(aq)

• O2(g) Æ O2(aq)

O2 dissolved in water Figure 3.08

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2 Common Monatomic Ions 3.2 Monatomic and Polyatomic Ions Common Monatomic Ions You must know the charges for all these ions.

• In Chapter 2 we saw that we can predict charges on some monatomic ions from their positions in the periodic table. • Look at the names of ions listed. Do you notice any patterns in their names?

13 14 13 Figure 3.12 14

Polyatomic Ions Ionic Compounds with Polyatomic Ions

• A polyatomic • Many ionic compounds contain a polyatomic consists of a group of anion: atoms with an overall – CaCO3, net charge. – NaHCO3, sodium • These two are also – NaCN, sodium cyanide called oxoanions – KNO3, nitrate because they contain because they contain • The only common polyatomic cation is the oxygen attached to ion, NH +: some other element. 4 – NH4NO3, ammonium nitrate

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Calcium carbonate is dissolved in hard Ionic Compounds water:

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3 Naming Polyatomic Ions Trends for Polyatomic Ions

• The name of the oxoanion ion changes when the number of oxygen atoms bonded to the central changes. Can you see any patterns?

Figure 3.17

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These are the ions listed on your in-class handout. You must memorize the ones in 3.3 Formulas for Ionic Compounds bold on the handout. • An ionic compound has no overall charge, so the charges on the cations and anions must cancel one another. This is the case in a pure substance, or when it is dissolved. • The formula that shows this ratio with the smallest whole numbers is called its .

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Writing Ionic Formulas Writing Ionic Formulas (Like Example 3.6)

• Write the formula for the compound that contains • Write the formulas for compounds each set of ions in the ratio given. containing the following ions: a) calcium ion and ion b) aluminum ion and ion c) sodium ion and ion d) sodium ion and sulfite ion e) ammonium ion and phosphate ion f) lithium ion and nitrate ion

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4 3.4 Naming Simple Ionic Compounds Common Monatomic Ions

Notice that all the metals are cations with charges that we could predict from the name of the compound they are in.

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Figure 3.23 Naming Ionic Compounds Containing Metals with Variable Charges

• What is the name of this • Many metals, including most of the transition metals, compound? can form more than one type of ion. When these metals are present in ionic compounds, and additional component must be added to the name to distinguish between similar compounds.

• How can we distinguish between CuO and Cu2O? • What is the difference between them? • Why do they combine in different ratios? ion diff

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What are the rules for naming these Some (not all) Charges for Metals that can compounds? have Ions of More than One Charge

29 30 29 Figure 3.25 30

5 Naming Ionic Compounds when Older Method for Naming… are Needed

• Name the following compounds a) MnO

b) MnO2

c) CuSO4

d) CrO3

e) Fe(NO3)3

You do not have to know how to use this method.

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3.5 Naming and Writing Formulas for Naming Molecular Compounds Molecular Compounds

• Because molecular compounds do not consist of ions, • Look at the formulas and the names of the molecular the nonmetals that compose them are in ratios that are compounds below. Can you determine the rules for difficult to predict. naming them? • Also, there are sometimes many different compounds composed of the same elements but just in different ratios or different number of atoms per :

• CO, CO2 • SO2, SO3 • NO, NO2, NO3, N2O, N2O4, N2O5

molecules 33 34

Prefixes used for Naming Molecular Naming Molecular Compounds Compounds

• Name the following compounds:

• SO3 name • SF6 • The mono prefix is not used for the first element in • N2O4 the compound. • CO • The mono prefix is not used for the second element PCl when there are no other compounds with the same • PCl5 combination of the elements. 35 36

6 Nonsystematic for Molecular Compounds Nonsystematic for Molecular Compounds 3.6 Acids and Bases (know these) 3.6 Acids and Bases

• Acids and bases exist as ions when dissolved in • Water – H2O water. Many bases are ionic compounds, but acids • Ammonia – NH3 are not – they are molecular compounds. How do • peroxide – H O acids form ions in solution when they are not 2 2 composed of ions?

• Acids form ions as a result of their interaction with water: HCl(g) Æ H+(aq) + Cl−(aq)

+ + • The H (aq) that forms actually exists as H3O (aq).

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Ionization of HCl in Water Bases ionize in water to form OH− ions

Cl−

+ H3O

Figure 3.30 39 40 39 Figure 3.33 40

Oxoacids Naming Binary Acids

• How are the first four acids similar and how are they named?

Acidic H

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7 Naming Binary Acids Naming Acids

• Why do some of the oxoacids have an -ic suffix while others have an -ous suffix? How can you predict the suffix?

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3.7 Predicting Properties and Naming acids Naming Compounds

• Name the following acids: • Before naming a compound, you must first a) HCl(aq) classify it as either an ionic compound, molecular compound, or acid. b) HNO3(aq) molecular compound, or acid. – If it is an ionic compound, you must also decide if c) HNO2(aq) – If it is an ionic compound, you must also decide if the cation is an ion that can vary in charge. d) H2SO4(aq) • These classifications allow you to name the compound with the proper rules.

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Naming Naming Compounds • Classify and then name the following: • Classify and then name • a) NO2 these compounds b) Mg3N2 c) CaSO4 d) H3PO4(aq) e) FeCl3

¾ Which of these does not form ions when dissolved in water? ¾ Which of these is most likely a gas at room temperature? ¾ Which of these is an electrolyte? 47 49

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