1

1

Chapter 3Chemical Compounds

• Ionic and Molecular Compounds

• Monatomic and Polyatomic Ions

• Formulas for Ionic Compounds

• Naming Ionic Compounds

• Naming and Writing Formulas for Molecular Compounds

• Acids and Bases

• Predicting Properties and Naming Compounds

3 -

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

2

Electrolytes and Nonelectrolytes

• Electrolytes

– substances that release ions when dissolved in water

• This process is also called dissociation or ionization

– conduct electricity

• Nonelectrolytes

– substances that do NOT dissociate in water

– do NOT conduct electricity

– Example: methanol

3 -

3

Electrolytes and Nonelectrolytes

3 -

2

4

Strong and Weak Electrolytes• Strong electrolytes

– dissociate completely into ions in water

– conduct electricity well

– Examples: NaCl and HCl

• Weak electrolytes

– do not dissociate completely into ions in water

– do not conduct electricity well

– Example: acetic acid

3 -

5

Strong and Weak Electrolytes

3 -

6

Ionic Compounds• Are composed of a metal cation and a nonmetal

anion

– Metals cations are

• positively charged ions

– Nonmetals anions are

• negatively charged ions

• Their cations and anions exist in proportions that give electrical neutrality

– These ions are arranged in a crystal lattice

• Also called salts

• Are one of the major categories of chemical compounds

3 -

3

7

Ionic Compounds

3 -

Figure 3.8

8

Molecular Compounds

• Are composed of 2 or more

nonmetals

• Have no overall charge

• Are the other major category of

chemical

compounds3 -

9

Table 3.1 Ionic and Molecular Compounds

3 -

Electrical conductivity poor

in pure form

Electrical conductivity is good

when compound is molten

Weak or nonelectrolyte in aqueous solution

Strong electrolyte in aqueous solution

Low densityHigh density

Low boiling pointVery high boiling point

Low melting pointVery high melting point

Soft solidHard, brittle solid

Gas, liquid, or solidCrystalline solid

Molecular CompoundsIonic Compounds

Properties of Ionic and Molecular Compounds

4

10

Practice – Ionic and Molecular Compounds

• Based on their formulas, which of the following are ionic compounds? Which are molecular compounds?1. O2

2. CaO

3. Na3N

4. NF3

• Which of the following compounds has a higher boiling point?1. KCl or CCl42. SO3 or Na2SO4

3. Cu3PO4 or P4O10

3 -

11

Practice Solutions – Ionic and Molecular Compounds

• Based on their formulas, which of the following are ionic compounds? Which

are molecular compounds?

1. O2 – molecular compound

2. CaO – ionic compound

3. Na3N – ionic compound

4. NF3 – molecular compound

3 -

12

Practice Solutions – Ionic and Molecular Compounds

• Which of the following compounds has a higher boiling point?

1. KCl or CCl4 – KCl (ionic compounds

have high boiling points)

2. SO3 or Na2SO4 – Na2SO4

3. Cu3PO4 or P4O10 – Cu3PO4

3 -

5

13

Monoatomic Ions• Are ions of a single atom

• Many are shown below on Figure 3.12 and Table 3.2

• Most main-group elements tend to form their ion charge based on how far away their group is from the noble gases

• Transition metals tend to form multiple charges

3 -

14

Polyatomic Ions• An ion containing 2 or more atoms, usually of more

than one element

• The most common are oxoanions, anions that contain oxygen attached to another element.

• Many are shown below on Figure 3.17 and Table 3.4 One polyatomic cation – NH4

+

3 -

15

Table 3.4 Important Polyatomic Anions

3 -

BO33-

PO33-

PO43-

O22-

C2O42-

CO32-

BorateMnO4-Permanganate

PhosphiteC2H3O2-Acetate

SO32-

SO42-

Cr2O72-

CrO42-

OH-

CN-

ClO-

ClO2-

ClO3-

ClO4-

HCO3-

NO2-

NO3-

PhosphateHydroxide

Ions with a -3 chargeCyanide

PeroxideHypochlorite

OxalateChlorite

CarbonateChlorate

SulfitePerchlorate

SulfateBicarbonate

DichromateNitrite

ChromateNitrate

Ions with a -2 chargeIons with a -1 charge

6

16

Writing Formulas for Ionic Compounds• When writing a formula for an ionic compound, the sum of

the positive charges must equal the sum of the negative charges.

Total positive charge + total negative charge = zero net charge

from cations from anions

• The crystal structures or lattices are composed of repeating units called formula units.

3 -

17

Practice – Writing Ionic Formulas

• Write the formulas for compounds containing the following ions:

1. Calcium ion and nitride ion

2. Barium ion and nitrate ion

3. Potassium ion and sulfate ion

3 -

18

Practice Solutions – Writing Ionic Formulas

• Write the formulas for compounds containing the following ions:1. Calcium ion and nitride ion

Ca2+ N3-

The least common denominator between +2 and -3 is 6. Therefore, this compound needs 3 calcium ions for every 2 nitride ions.

Answer: Ca3N2

2. Barium ion and nitrate ionBa2+ NO3

-

The least common denominator between +2 and -1 is 2. Therefore, this compound needs 1 barium ion for every 2 nitrate ions.

Answer: Ba(NO3)2

3 -

7

19

Practice Solutions – Writing Ionic Formulas

• Write the formulas for compounds containing the following ions:

3. Potassium ion and sulfate ionK+ SO4

2-

The least common denominator between +1 and -2 is 2. Therefore, this compound needs 2 potassium ions for every 1 sulfate ion.

Answer: K2SO4

3 -

20

Practice – Naming Ionic Compounds

• Now that you have translated the ion names into an ionic formula, translate the formula into the ion names.

1. NaCl

2. NaNO2

3. MgCl24. Mg(NO3)2

5. BaO

6. Li3N

3 -

21

Practice Solutions – Naming Ionic Compounds

• Now that you have translated the ion names into an ionic formula, translate the formula into the ion names.

1. NaCl – sodium ion and chloride ion (name: sodium chloride) Na+ and Cl-

2. NaNO2 – sodium ion and nitrite ion

(name: sodium nitrite) Na+ and NO2-

3. MgCl2 – magnesium ion and chloride ion (name: magnesium chloride) Mg2

+ and Cl-

3 -

8

22

Practice Solutions – Naming Ionic Compounds

• Now that you have translated the ion names into an ionic formula, translate the formula into the ion names.

4. Mg(NO3)2 – magnesium ion and nitrate ion (name: magnesium nitrate)

5. BaO – barium ion and oxide ion

(name: barium oxide)

6. Li3N – lithium ion and nitride ion

(name: lithium nitride)

3 -

23

Naming Ionic Compounds• Naming metals

– Monatomic cations are named according to the periodic table• Transition metals

(and Sn and Pb) require a Roman numeral in parenthesis to designate their charge (using the Stock System)

3 -

Metals –Name according

to periodic table

Main-GroupDo nothing more

Transition Write Roman numeral telling

charge

24

Naming Ionic Compounds• Naming nonmetals

– Monatomic anions

1. Name according to the periodic table

2. Drop the ending

3. Add an –ide

– Polyatomic anions

• Name according to

the Polyatomic Ion Chart (Table 3.4)

3 -

Nonmetals

MonatomicDrop ending and

add “-ide”

PolyatomicName according

to Table 3.4

9

25

Naming Ionic Compounds Summary Main Group Metals

3 -

26

Naming Ionic Compounds Summary Transition Metals

3 -

NH4+

27

Common Names for Metals with Variable Charges

• An older naming system exists for

transition metals (and Sn and Pb)

based on the roots of the original

Latin names.

• The smaller charge has an “-ous”

ending.

• The larger charge has an “-ic”

ending.3 -

10

28

Common Names for Metals with Variable Charges

3 -

stannic oxidetin(IV) oxideSn+4SnO2

stannous oxide

cupric oxide

cuprous oxide

ferric chloride

ferrous chloride

Old Name

Sn+2

Cu+2

Cu+1

Fe+3

Fe+2

Ion

tin(II) oxide

copper(II) oxide

copper(I) oxide

iron(III) chloride

iron(II) chloride

Stock Name

SnO

CuO

Cu2O

FeCl3

FeCl2

Compound

Table 3.7 Names of Ionic Compounds Containing Metals with Variable Charges

29

Practice – Naming Molecular Compounds

• Do you see the pattern? Try naming these

compounds as well.

1. SO2

2. NF3

3. P4O10

3 -

phosphorus

pentafluoride

dinitrogen tetroxide

sulfur trioxide

Name

PF5

N2O4

SO3

Formula

carbon tetrachloride

carbon dioxide

carbon monoxide

Name

CCl4

CO2

CO

Formula

Names of Some Common Molecular Compounds

30

Practice Solutions – Naming Molecular Compounds

• Try naming these compounds as well…

1. SO2 – sulfur dioxide

2. NF3 – nitrogen trifluoride

3. P4O10 – tetraphosphorus decoxide

3 -

phosphorus

pentafluoride

dinitrogen tetroxide

sulfur trioxide

Name

PF5

N2O4

SO3

Formula

carbon tetrachloride

carbon dioxide

carbon monoxide

Name

CCl4

CO2

CO

Formula

Names of Some Common Molecular Compounds

11

31

Naming Molecular Compounds• We will name binary molecular compounds

– Binary Compounds

• A compound containing atoms or ions of only two elements

• To name molecular compounds, we:

1. Name the leftmost element as we would a main-group metal – according to the periodic table.

2. Name the rightmost element as we would a monatomic anion – drop the ending of the name (from the periodic table) and add an “-ide”.

3. Use Greek prefixes to denote the number of atoms of each element.

3 -

32

Naming Molecular Compounds

3 -

8octa -3tri -

7hepta -2di -

deca -

nona -

hexa -

Prefix

10

9

6

Name

5

4

1

Name

penta -

tetra -

mono -

Prefix

Table 3.9 Common Greek Prefixes

33

Naming Molecular Compounds Summary

3 -

12

34

Acids and Bases• Acids

– Are substances that when dissolved in water provide hydrogen ions (H+)

– An example of the dissociation (or ionization) of an acid:

HCl(g) → H+(aq) + Cl-(aq)

• Bases– Are substances that react

with acids in aqueous solution to form water

– An example of the ionization of a base:

NaOH(s) → Na+(aq) + OH-(aq)3 -

H2O

H2O

35

Naming Acids

3 -

Hypochlorous

acidHClO(aq)Nitric acidHNO3(aq)

Chlorous acid

Chloric acid

Perchloric acid

Sulfurous acid

Sulfuric acid

Name

HClO2(aq)

HClO3(aq)

HClO4(aq)

H2SO3(aq)

H2SO4(aq)

Formula

Carbonic acid

Hydrosulfuric

acid

Hydroiodic acid

Hydrochloric acid

Hydrofluoric acid

Name

H2CO3(aq)

H2S(aq)

HI(aq)

HCl(aq)

HF(aq)

Formula

Table 3.11 Names of Some Common Acids

36

Naming Acids• Since most acids have a hydrogen as their 1st

element in the molecular formula, the acids are named according to the anion, not the cation (H+).

• Binary acids are named as hydro- followed by the root of the element (2nd element or anion) name with an –ic suffix and the word acid placed at the end of the name.

• Acids containing polyatomic ions (as the anion) are named by taking the root of the polyatomic ion name, replacing –ate with –ic or replacing –ite with –ous and adding the word acid at the end.

3 -

13

37

Naming Acids Summary

3 -

38

Practice – Naming Molecular Compounds

• Name the following binary molecular compounds:

1. OF2

2. SiCl43. P4O6

• Name the following acids:

1. HBr(aq)

2. HMnO4(aq)

3. H3PO3(aq)

3 -

39

Practice Solutions – Naming Molecular Compounds

• Name the following binary molecular compounds:

1. OF2 – oxygen difluoride

2. SiCl4 – silicon tetrachloride

3. P4O6 – tetraphosphorus hexoxide

• Name the following acids:

1. HBr(aq) – hydrobromic acid

2. HMnO4(aq) – permanganic acid

3. H3PO3(aq) – phosphoric acid

3 -

14

40

Naming Compounds Summary

3 -

41

Naming Compounds Summary

3 -

Naming

Binary acids are named as hydro- followed by the root of the element name with an –ic suffix and the

word acid placed at the end of the name.

Acids containing polyatomic ions are named by taking the root of the polyatomic ion name,

replacing –ate with –ic or replacing –ite with –ousand adding the word acid at the end.

1st atom in formula (the element farther down or to the left in the periodic table) named 1st

with the second element named as if it were

an anion. Greek prefixes are used to

designate the number of atoms in a molecule.

Cation named first followed by anion

Acids

Molecular

Ionic

Type of Compound

42

Practice – Naming Compounds

• Name the following compounds:1. Al2S3

2. HNO2(aq)

3. HI(aq)

4. P2O5

5. Cu(OH)2

6. H2SO3(aq)

7. K2O

8. CS2

9. (NH4)2CO3

10. Fe(C2H3O2)3

3 -

15

43

Practice Solutions – Naming Compounds

• Name the following compounds:1. Al2S3 – aluminum sulfide

2. HNO2(aq) – nitrous acid

3. HCl(aq) – hydrochloric acid

4. P2O5 – diphosphorus pentoxide

5. Cu(OH)2 – copper(II) hydroxide

6. H2SO3(aq) – sulfurous acid

7. K2O – potassium oxide

8. CS2 – carbon disulfide

9. (NH4)2CO3 – ammonium carbonate

10. Fe(C2H3O2)3 – iron(III) acetate

3 -

44

Practice – Naming Compounds

• Write the compound formulas for the following

names:

1. Lead(II) chloride

2. Magnesium phosphate

3. Nitrogen triiodide

4. Hydrofluoric acid

5. Tin(IV) oxide

6. Calcium nitride

7. Cyanic acid

8. Dichlorine pentoxide

9. Sodium hydrogen carbonate

10. Hydrogen peroxide

3 -

45

Practice Solutions – Naming Compounds

• Write the compound formulas for the following

names:

1. Lead(II) chloride – PbCl22. Magnesium phosphate – Mg3(PO4)2

3. Nitrogen triiodide – NI34. Hydrofluoric acid – HF(aq)

5. Tin(IV) oxide – SnO2

6. Calcium nitride – Ca3N2

7. Cyanic acid – HCN(aq)

8. Dichlorine pentoxide – Cl2O5

9. Sodium hydrogen carbonate – NaHCO3

10. Hydrogen peroxide – H2O2

3 -