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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
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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
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Electrolytes and Nonelectrolytes
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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
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Strong and Weak Electrolytes
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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
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Ionic Compounds
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Figure 3.8
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Molecular Compounds
• Are composed of 2 or more
nonmetals
• Have no overall charge
• Are the other major category of
chemical
compounds3 -
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Table 3.1 Ionic and Molecular Compounds
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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
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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
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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
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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
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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
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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
+
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Table 3.4 Important Polyatomic Anions
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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
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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.
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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
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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
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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
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Practice Solutions – Writing Ionic Formulas
• Write the formulas for compounds containing the following ions:
3. Potassium ion and sulfate ionK+ SO4
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The least common denominator between +1 and -2 is 2. Therefore, this compound needs 2 potassium ions for every 1 sulfate ion.
Answer: K2SO4
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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
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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-
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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)
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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)
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Metals –Name according
to periodic table
Main-GroupDo nothing more
Transition Write Roman numeral telling
charge
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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)
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Nonmetals
MonatomicDrop ending and
add “-ide”
PolyatomicName according
to Table 3.4
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Naming Ionic Compounds Summary Main Group Metals
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Naming Ionic Compounds Summary Transition Metals
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NH4+
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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”
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Common Names for Metals with Variable Charges
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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
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Practice – Naming Molecular Compounds
• Do you see the pattern? Try naming these
compounds as well.
1. SO2
2. NF3
3. P4O10
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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
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Practice Solutions – Naming Molecular Compounds
• Try naming these compounds as well…
1. SO2 – sulfur dioxide
2. NF3 – nitrogen trifluoride
3. P4O10 – tetraphosphorus decoxide
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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
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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.
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Naming Molecular Compounds
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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
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Naming Molecular Compounds Summary
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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
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Naming Acids
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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
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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.
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Naming Acids Summary
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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)
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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
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Naming Compounds Summary
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Naming Compounds Summary
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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
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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
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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
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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
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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
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