Download Chapter 6 Ionic and Molecular Compounds

10/12/2015
Chapter 6 Readiness
Lecture Presentation
Key Math Skills
Chapter 6
Ionic and
Molecular
Compounds
Karen C. Timberlake
General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake
© 2016 Pearson Education, Inc.
Chapter 6 Why do atoms react?
• Using Positive and Negative Numbers in
Calculations (1.4B)
• Solving Equations (1.4D)
Core Chemistry Skills
• Writing Electron Configurations (4.7)
• Drawing Lewis Symbols (4.8)
Chapter 6 Why do atoms react?
• Recall the chemical properties of the noble
gases – they are extremely unreactive
Completely filled
valence energy level
• What do they have in common that could be
the cause of this lack of reactivity?
• Examination of their electron configurations
reveals that the noble gases either have
1. an outermost electron energy level that is
completely filled with electrons (He = 2 e- in the
1st energy level, Ne = 8 e- in the 2nd energy
level)
General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake
© 2016 Pearson Education, Inc.
General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake
© 2016 Pearson Education, Inc.
8 valence electrons
OR:
2. 8 electrons in the outermost energy level (8
valence e-)
General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake
© 2016 Pearson Education, Inc.
Chapter 6 Why do atoms react?
6.1 Ions: Transfer of Electrons
• It is this arrangement of electrons that
imparts stability to the noble gases
Atoms form positively charged ions when they lose electrons and
negatively charged ions when they gain electrons.
• All other elements react in order to achieve
the same electron configuration as their
nearest noble gas neighbor (8 valence e- =
octet rule)
Ionic bonds are formed by the strong attractive forces between positive
and negative ions.
Learning Goal Write the symbols for the simple ions of the
representative elements.
• Atoms can gain, lose, or share electrons in
order to achieve the same electronic
structure as their nearest noble gas neighbor
General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake
© 2016 Pearson Education, Inc.
General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake
© 2016 Pearson Education, Inc.
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10/12/2015
Ionic and Covalent Bonds
Ionic and Covalent Bonds
Chemical bonds are formed when atoms lose, gain,
or share valence electrons to acquire an octet of
eight valence electrons (octet rule).
• Ionic bonds occur when valence electrons of a
metal atom are transferred to the atom of a
nonmetal.
• Covalent bonds occur when nonmetal atoms
share electrons to attain a noble gas arrangement.
General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake
© 2016 Pearson Education, Inc.
General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake
© 2016 Pearson Education, Inc.
Positive Ions: Metals Lose Electrons
Positive Ions: Loss of Electrons
In ionic bonding, ions form when atoms gain or
lose their valence electrons to form a stable
electron configuration. Metals in Group 1A (1),
Group 2A (2), and Group 3A (13)
Sodium atoms in Group 1A (1) are neutral, with 11 electrons and
11 protons, they
• lose one electron to have the same number of valence electrons
as neon and a filled energy level.
• will form an ion with 10 electrons, 11 protons, and an ionic charge
of 1+: Na+.
• have low ionization energies, which means it
doesn’t take much energy to remove an e• readily lose one or more of their valence electrons
to form ions with a positive charge.
• lose electrons until they have the same number of
valence electrons as the nearest noble gas, usually
eight valence electrons.
General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake
© 2016 Pearson Education, Inc.
General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake
© 2016 Pearson Education, Inc.
Positive Ions: Loss of Electrons
Negative Ions: Nonmetals Gain Electrons
Magnesium atoms in Group 2A (2) are neutral, and they have
12 electrons and 12 protons. They
• will lose 2 electrons to have the same number of valence
electrons as neon and a filled energy level.
• form an ion with 10 electrons, 12 protons, and an ionic charge of
2+: Mg2+.
Nonmetals, Group 5A (15), Group 6A (16), and
Group 7A (17)
• have high ionization energies, they don’t tend to lose
electrons but instead gain electrons
• readily gain one or more valence electrons to form
ions with a negative charge.
• gain electrons until they have the same number of
valence electrons as the nearest noble gas, usually
eight valence electrons.
Core Chemistry Skill Writing Symbols For Positive
and Negative Ions
General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake
© 2016 Pearson Education, Inc.
General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake
© 2016 Pearson Education, Inc.
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Negative Ions: Gain of Electrons
Formulas, Names of Common Ions
Chlorine atoms in Group 7A (17) are neutral, and they have
17 electrons and 17 protons. They
• will gain one electron to have the same number of valence
electrons as argon.
• form an ion with 18 electrons, 17 protons, and a charge of 1−: Cl−.
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Karen C. Timberlake
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Ionic Charges, Group Numbers
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Karen C. Timberlake
Chemistry Link to Health: Important Ions in
the Body
We can use the group numbers in the periodic table to determine
the charges for the ions of the representative elements.
Ions are important in regulating body functions.
Ion
Occurrence
Function
Source
Na+
Principal cation
outside the cell
Regulation and control of
body fluids
Salt, cheese,
pickles
K+
Principal cation
outside the cell
Regulation of body fluids
and cellular functions
Bananas, potatoes,
orange juice, milk
Ca2+
Cation outside the Major cation in bones,
cell; found in bones needed for muscle
contractions
Mg2+ Cation outside the Essential for certain
cell; found in bones enzymes, muscles, and
nerve control
General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake
© 2016 Pearson Education, Inc.
© 2016 Pearson Education, Inc.
General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake
Milk, yogurt,
cheese, greens,
spinach
Chlorophyll, nuts,
grains
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Study Check
Study Check
Write the formula and symbol of an ion with
16 protons and 18 electrons.
Consider the elements calcium and chlorine.
A. Identify each as a metal or a nonmetal.
B. State the number of valence electrons
for each.
C. State the number of electrons that must be
lost or gained for each to acquire
an octet.
D. Write the symbol, including its ionic charge,
and name of each resulting ion.
General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake
© 2016 Pearson Education, Inc.
General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake
© 2016 Pearson Education, Inc.
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6.2 Writing Formulas for Ionic Compounds
Properties of Ionic Compounds
Ionic compounds consist of
positive and negative charges
held together by the strong
electrical attractions between
oppositely charged ions.
Ionic compounds
• consist of positive and negative ions.
• have attractions called ionic bonds between
positively and negatively charged ions.
• have high melting points.
• are solids at room temperature.
Learning Goal Using charge
balance, write the correct formula
for an ionic compound.
General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake
© 2016 Pearson Education, Inc.
General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake
© 2016 Pearson Education, Inc.
NaCl, An Ionic Compound
Formulas of Ionic Compounds
Sodium chloride is
more commonly
known as table salt.
The magnification of
NaCl crystals shows
the arrangement of
Na+ and Cl− ions in
an NaCl crystal.
In a chemical formula,
• the symbols and subscripts are written in the lowest
whole-number ratio of the atoms or ions.
• the sum of ion charges equals zero.
• the total positive charge = total negative charge.
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Karen C. Timberlake
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Subscripts in Formulas
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Karen C. Timberlake
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Writing Ionic Formulas from Ion Charges
To balance ionic charge in an ionic compound,
total positive charge = total negative charge
Core Chemistry Skill Writing Ionic Formulas
General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake
© 2016 Pearson Education, Inc.
General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake
© 2016 Pearson Education, Inc.
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Study Check
Study Check
Write the ionic formula of the compound formed
with Ba2+ and Cl− ions.
Select the correct formula for each of the
following ionic compounds.
1. Na+ and O2−
A. NaO
B. Na2O
C. NaO2
2. Al3+ and Cl−
A. AlCl3
B. AlCl
C. Al3Cl
3. Mg2+ and N3−
A. MgN
B. Mg2N3
C. Mg3N2
General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake
© 2016 Pearson Education, Inc.
General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake
© 2016 Pearson Education, Inc.
6.3 Naming and Writing Ionic Compounds
Naming Ionic Compounds
Iodized salt contains Kl,
potassium iodide, to prevent
iodine deficiency.
When naming an ionic compound,
• the name of the metal is written first and is the
same as the name of the element.
• the name of the nonmetal is the first syllable
of the nonmetal name + ide ending and is
written second.
• a space is placed between the name of the metal
and nonmetal ion.
Learning Goal Given the
formula of an ionic compound,
write the correct name; given
the name of an ionic compound,
write the correct formula.
Core Chemistry Skill Naming Ionic Compounds
General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake
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Names of Some Ionic Compounds
General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake
General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake
© 2016 Pearson Education, Inc.
Guide to Naming Ionic Compounds
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General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake
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Naming Ionic Compounds, K2O
Naming Ionic Compounds, K2O
Name the ionic compound K2O.
STEP 1 Identify the cation and anion.
The cation, K+, is from Group 1A (1),
and the anion, O2−, is from Group 6A
(16).
STEP 2 Name the cation by its
element name.
The cation, K+, is potassium.
Name the ionic compound K2O.
STEP 3 Name the anion by using the first
syllable of its element name
followed by ide.
The name of the anion is oxide.
STEP 4 Write the name for the cation first
and the name for the anion second.
K2O is potassium oxide.
General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake
© 2016 Pearson Education, Inc.
General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake
Study Check
Solution
Write the names of the following compounds.
A. CaO ___________
B. Al2O3 ___________
C. MgCl2 ___________
Write the names of the following compounds.
© 2016 Pearson Education, Inc.
STEP 1 Identify the cation and anion.
A. CaO: The cation, Ca2+, is from Group 2A (2),
and the anion, O2−, is from Group 6A (16).
B. Al2O3: The cation, Al3+, is from Group 3A (13),
and the anion, O2−, is from Group 6A (16).
C. MgCl2: The cation, Mg2+, is from Group 2A (2),
and the anion, Cl−, is from Group 7A (17).
General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake
© 2016 Pearson Education, Inc.
General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake
© 2016 Pearson Education, Inc.
Solution
Solution
Write the names of the following compounds.
Write the names of the following compounds.
STEP 2 Name the cation by its element name.
A. CaO: The cation, Ca2+, is calcium.
STEP 3 Name the anion by using the first
syllable of its element name followed
by ide.
A. CaO: The anion, O2−, is oxide.
B. Al2O3: The cation, Al3+, is aluminum.
B. Al2O3: The anion, O2−, is oxide.
C. MgCl2: The cation, Mg2+, is magnesium.
C. MgCl2: The anion, Cl−, is chloride.
General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake
© 2016 Pearson Education, Inc.
General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake
© 2016 Pearson Education, Inc.
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Solution
Study Check
Write the names of the following compounds.
Write the formulas and names for compounds
of the following ions:
Br−
S2−
N3−
STEP 4 Write the name of the cation first and
the name of the anion second.
A. The name of CaO is calcium oxide.
Na+
B. The name of Al2O3 is aluminum oxide.
Al3+
C. The name of MgCl2 is magnesium
chloride.
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General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake
Metals with Variable Charge
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Karen C. Timberlake
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Metals with Variable Charge
Transition metals except for Zn2+, Cd2+, and Ag+
form two or more positive ions (cations).
A Roman numeral equal to the ion charge is placed
in parentheses immediately after the metal name.
Cu2+
Cu+
Fe2+
Fe3+
copper(II)
copper(I)
iron(II)
iron(III)
Pb2+
Pb4+
Cr2+
Cr3+
lead(II)
lead(IV)
chromium(II)
chromium(III)
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Karen C. Timberlake
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Determination of Variable Charge
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Ion Charges, Periodic Table
Use the charge on the anion and charge
balance to calculate charge on the metal ion.
MnF2
Mn charge + 2 F− charge = 0
? + 2 (1−) = 0
2+ + 2−
=0
Manganese(II) fluoride
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General, Organic, and Biological Chemistry: Structures of Life, 5/e
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Guide to Naming Ionic Compounds with
Variable Charge Metals
Naming Ionic Compounds with Variable
Charge Metals, FeCl2
Name the ionic compound FeCl2.
STEP 1 Determine the charge of the cation from
the anion.
Formula
ANALYZE THE Elements
PROBLEM
Groups
Ions
Charge
Balance
Ions
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Karen C. Timberlake
Naming Ionic Compounds with Variable
Charge Metals, FeCl2
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Karen C. Timberlake
Metal
FeCl2
iron (Fe) chloride
transition element
Fe?
Fe?
+
1(?)
+
2+
Fe
Nonmetal
(Cl)
Group 7A (17)
Cl−
2(1−) = 0
2(1−) = 0
Cl−
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Study Check
Name the following ionic compound containing
a variable charge metal. SnO2
Name the ionic compound FeCl2.
STEP 2 Name the cation by its element name, and
use a Roman numeral in parentheses for
the charge. iron(II)
STEP 3 Name the anion by using the first syllable of
its element name followed by ide. chloride
STEP 4 Write the name for the cation first and the
anion second. iron(II) chloride
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General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake
General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake
© 2016 Pearson Education, Inc.
Solution
Solution
Name the following ionic compound containing a
variable charge metal. SnO2
Name the following ionic compound containing a
variable charge metal. SnO2
STEP 1 Determine the charge of the cation from
the anion.
STEP 2 Name the cation by its element name and
use a Roman numeral in parentheses for
the charge. tin(IV)
STEP 3 Name the anion by using the first syllable
of its element name followed by ide. oxide
STEP 4 Write the name for the cation first and the
anion second. tin(IV) oxide
ANALYZE THE
PROBLEM
Formula
Elements
Groups
Ions
Charge
Balance
Ions
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Karen C. Timberlake
Metal
SnO2
tin (Sn)
transition element
Sn?
Sn?
+
1(?)
+
Sn4+
Nonmetal
oxide (O)
Group 6A (16)
O2−
2(2−) = 0
2(2−) = 0
O2−
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General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake
© 2016 Pearson Education, Inc.
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Writing Formulas from the Name of an Ionic
Compound
Guide to Writing Formulas from the Name of
an Ionic Compound
The formula for an ionic
compound is written from,
• the first part of the
name that describes
the metal ion.
• the second part of the
name that specifies the
nonmetal ion.
Subscripts are added to
balance the charge.
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General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake
General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake
© 2016 Pearson Education, Inc.
Writing Formulas from the Name of an Ionic
Compound
Writing Formulas from the Name of an Ionic
Compound
Write the formula for iron(III) chloride.
Write the formula for iron(III) chloride.
STEP 1 Identify the cation and anion.
STEP 2 Balance the charges.
Fe3+
Cl−
Cl−
Cl−
1(3+) + 3(1−) = 0
ANALYZE
THE
PROBLEM
Type of Ion
Name
Group
Symbol of Ion
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Cation
iron(III)
transition element
Fe3+
Anion
chloride
Group 7A (17)
Cl−
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Becomes the subscript in the chemical formula.
STEP 3 Write the formula, cation first, using
subscripts from the charge balance. FeCl3
General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake
© 2016 Pearson Education, Inc.
Study Check
Solution
Write chemical formulas for the following
compounds:
A. nickel(II) sulfide
B. zinc chloride
C. iron(III) oxide
Write chemical formulas for the following compounds.
General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake
© 2016 Pearson Education, Inc.
STEP 1 Identify the cation and anion.
A. nickel(II) sulfide
The Roman numeral (II) indicates that the charge
on the nickel ion is 2+, Ni2+. The anion sulfide S2−.
B. zinc chloride
Zinc is one of the transition metals with a fixed
charge of 2+, Zn2+. The anion chloride is Cl−.
C. iron(III) oxide
The Roman numeral (III) indicates that the charge
on the iron ion is 3+, Fe3+. The anion oxide is O2−.
General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake
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Solution
Solution
Write chemical formulas for the following compounds.
Write chemical formulas for the following compounds.
STEP 2 Balance the charges.
A. nickel(II) sulfide
Ni2+ S2−
1(2+) + 1(2−) = 0
STEP 3 Write the formula, cation first, using
subscripts from the charge balance.
A. nickel(II) sulfide NiS
B. zinc chloride
ZnCl2
C. iron(III) oxide
Fe2O3
B. zinc chloride
Zn2+ Cl−
Cl−
1(2+) + 2(1−) = 0
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C. iron(III) oxide
Fe3+ O2−
Fe3+
O2−
O2−
2(3+) + 3(2−) = 0
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General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake
© 2016 Pearson Education, Inc.
6.4 Polyatomic Ions
Polyatomic Ions
Sodium chlorite, NaClO2, is
used in the processing and
bleaching of pulp from
wood fibers and recycled
cardboard.
Polyatomic ions
• are a group of atoms with an overall charge.
• often consist of a nonmetal such as
phosphorus, sulfur, carbon, or nitrogen and
oxygen.
• usually have a 1−, 2−, or 3− charge.
• have a negative charge, except for NH4+,
ammonium, which has a positive charge,
Learning Goal Write the
name and formula for an
ionic compound containing
a polyatomic ion.
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Karen C. Timberlake
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Polyatomic Ions
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Polyatomic Ions, Names, and Formulas
Many products contain polyatomic ions, which are
groups of ions that have an ionic charge.
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Names of Polyatomic Ions
Names of Polyatomic Ions
1. Names of most common polyatomic ions end in ate.
SO42− sulfate
PO43− phosphate
NO3− nitrate
3. Exceptions to these rules are the following:
cyanide
CN−
OH−
hydroxide
2. When a related ion has one less oxygen, its name
ends in ite.
SO32− sulfite
PO33− phosphite
NO2− nitrite
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General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake
Names of Polyatomic Ions
5. Halogens form 4 polyatomic
ions with oxygen.
Each has a −1 charge.
ClO4−
perchlorate
ClO3−
chlorate
ClO2−
chlorite
ClO−
hypochlorite
4. Add an H+ to the polyatomic
+ H+ =
CO32−
carbonate
+ H+ =
SO42−
+ H+ =
sulfate
+ H+ =
ion, and add +1 to its charge.
HCO3−
bicarbonate or hydrogen carbonate
HSO4−
bisulfate or hydrogen sulfate
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General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake
Writing Formulas for Compounds
Containing Polyatomic Ions
When writing formulas for ionic compounds containing
polyatomic ions, we use the same rules of charge balance as
those for simple ionic compounds.
Consider the formula for magnesium nitrate:
Sodium chlorite is used in the
processing and bleaching of pulp from
wood fibers and recycled cardboard.
General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake
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Guide to Writing Formulas with
Polyatomic Ions
Magnesium ion
Nitrate ion
Mg2+
+
(2+)
Mg2+
+
+
NO3−
NO3−
2(1−)
2 NO3−
Parentheses are placed around the
polyatomic ion, and the subscript is
placed just outside the parentheses.
= 0
= Mg(NO3)2
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Karen C. Timberlake
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Writing Formulas with Polyatomic Ions,
Aluminum Bicarbonate
Write the formula for aluminum bicarbonate.
STEP 1 Identify the cation and polyatomic ion (anion).
Cation
Polyatomic ion
Al3+
HCO3−
STEP 2 Balance the charges.
Al3+
HCO3−
HCO3−
HCO3−
1(3+) +
3(1−) = 0
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Karen C. Timberlake
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Writing Formulas with Polyatomic Ions,
Aluminum Bicarbonate
Study Check
Write the formula for sodium phosphate.
Write the formula for aluminum bicarbonate.
STEP 3 Write the formula, cation first, using
the subscripts from charge balance.
Al(HCO3)3
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Karen C. Timberlake
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General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake
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Solution
Solution
Write the formula for sodium phosphate.
Write the formula for sodium phosphate.
STEP 1 Identify the cation and polyatomic ion (anion).
Cation
Polyatomic ion
Na+
PO43−
STEP 2 Balance the charges.
Na+
PO43−
Na+
Na+
3(1+) +
1(3−) = 0
General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake
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Naming Compounds with Polyatomic Ions
STEP 3 Write the formula, cation first, using
the subscripts from charge balance.
Na3PO4
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Karen C. Timberlake
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Compounds with Polyatomic Ions
When naming ionic compounds containing polyatomic ions,
• first write the positive ion, usually a metal.
• write the name of the polyatomic ion second.
Recognizing polyatomic ions in a chemical formula helps to
name it correctly. As with other ionic compounds, no prefixes
are used.
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Karen C. Timberlake
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Study Check
Guide to Naming Compounds with
Polyatomic Ions
Select the correct formula for each.
1. aluminum nitrate
A. AlNO3
B. Al(NO) 3
C. Al(NO3) 3
2. copper(II) nitrate
A. CuNO3
B. Cu(NO3)2 C. Cu2 (NO3)
3. iron(III) hydroxide
A. FeOH
B. Fe3OH
C. Fe(OH)3
4. tin(IV) hydroxide
B. Sn(OH)2
C. Sn4(OH)
A. Sn(OH)4
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General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake
Flow Chart, Naming Ionic Compounds
General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake
© 2016 Pearson Education, Inc.
Study Check
Name the following ionic compounds:
A. Ca(NO3)2
B. FePO4
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Karen C. Timberlake
Solution
Ca2+
B. FePO4
Fe3+
© 2016 Pearson Education, Inc.
Study Check
Name the following ionic compounds:
STEP 1
STEP 2 STEP 3
Identify
Name
Name
cation/anion
cation
anion
A. Ca(NO3)2
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Karen C. Timberlake
NO3−
PO4
3−
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Karen C. Timberlake
STEP 4
Name
compound
Name each of the following compounds
containing polyatomic ions.
A. MgSO3
calcium nitrate
B. MgSO4
calcium
nitrate
iron(III)
phosphate iron(III) phosphate
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C. Pb3(PO3)2
General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake
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Study Check
6.5 Molecular Compounds: Sharing
Electrons
Name each of the following compounds:
A. Fe2(SO4)3
B. Ba3(PO3)2
C. NiCO3
The names of molecular
compounds need prefixes
because several different
compounds can be formed from
the same two nonmetals.
Learning Goal Given the
formula of a molecular
compound, write its correct name;
given the name of a molecular
compound, write its formula.
General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake
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Covalent Bonds
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Names and Formulas, Molecular
Compounds
Molecular compounds form when
• atoms of two or more nonmetals share electrons
and form a covalent bond.
• valence electrons are shared by nonmetal atoms
to achieve stability.
A molecule forms when two or more atoms share
electrons.
Core Chemistry Skill Writing the Names and
Formulas for Molecular Compounds
General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake
General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake
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Names and Formulas, Molecular
Compounds
When naming a molecular
compound, the
• first nonmetal in the
formula is named by its
element name.
• second nonmetal is named
using the first syllable of
the name followed by ide.
When a subscript indicates
two or more atoms of an
element, a prefix is shown in
front of its name.
General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake
© 2016 Pearson Education, Inc.
Common Molecular Compounds
Several compounds may be formed from the
same two nonmetals:
CO2
= carbon dioxide
CO
= carbon monoxide
• The number of oxygen atoms present is
indicated by the prefix.
• When the vowels o and o or a and o appear
together, the first vowel is omitted.
NO
= nitrogen monoxide,
General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake
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General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake
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Guide to Naming Molecular Compounds
Naming Molecular Compounds, NCl3
Name the molecular compound NCl3.
ANALYZE THE
PROBLEM
Symbol of the Element
Name
Subscript
Prefix
N
nitrogen
1
none
Cl
chloride
3
tri
STEP 1 Name the first nonmetal by its element name.
In NCl3, the first nonmetal (N) is nitrogen.
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General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake
General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake
Naming Molecular Compounds, NCl3
Study Check
Name the molecular compound NCl3.
Name the molecular compound B2O3.
© 2016 Pearson Education, Inc.
STEP 2 Name the second nonmetal by using the first
syllable of the element name followed by ide.
In NCl3, the second nonmetal (Cl) is chloride.
STEP 3 Add prefixes to indicate the number of atoms
(subscripts).
Because there is one nitrogen atom, no prefix is
needed. The subscript 3 for the Cl atoms is shown
as the prefix tri.
The name of NCl3 is nitrogen trichloride.
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General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake
General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake
Solution
Solution
Name the molecular compound B2O3.
Name the molecular compound B2O3.
ANALYZE THE
PROBLEM
Symbol of the Element
Name
Subscript
Prefix
B
boron
2
di
O
oxide
3
tri
STEP 1 Name the first nonmetal by its element name.
In B2O3, the first nonmetal (B) is boron.
STEP 2 Name the second nonmetal by using the first
name followed by ide.
The name of the second nonmetal (O) is oxide.
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Karen C. Timberlake
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STEP 3 Add prefixes to indicate the number of
atoms (subscripts).
In B2O3, the first nonmetal (B) has the
subscript of 2, which is shown as the prefix di.
The subscript of 3 for the O atoms is shown as
the prefix tri.
The name of B2O3 is diboron trioxide.
General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake
© 2016 Pearson Education, Inc.
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Guide to Writing Formulas from the Names
of Molecular Compounds
Study Check
Write the molecular formula for diphosphorus
pentoxide.
General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake
© 2016 Pearson Education, Inc.
General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake
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Solution
Compounds, Ionic or Covalent?
Write the molecular formula for diphosphorus
pentoxide.
A compound is usually
• ionic if the first element in the formula or the
name is a metal or the polyatomic ion NH4+.
K2O: K is a metal; the compound is ionic.
potassium oxide
• covalent if the first element in the formula is a
nonmetal.
N2O: N is a nonmetal; the compound is
covalent.
dinitrogen oxide
STEP 1 Write the symbols in the order of the
elements in the name.
STEP 2 Write any prefixes as subscripts. The
prefix di in diphosphorus indicates there
are two phosphorus atoms. The prefix
penta in pentoxide indicates there are five
oxygen atoms. P2O5
General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake
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Flowchart, Naming Compounds
General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake
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Study Check
Select the correct name for each compound.
General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake
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1. SiCl4
A. silicon chloride
B. tetrasilicon chloride
C. silicon tetrachloride
2. P2O5
A. phosphorus oxide
B. phosphorus pentoxide
C. diphosphorus pentoxide
3. Cl2O7
A dichlorine heptoxide
B. dichlorine oxide
C. chlorine heptoxide
General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake
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Study Check
6.6 Lewis Structures for Molecules and
Polyatomic Ions
Identify each compound as ionic or covalent
and give its correct name.
A. SO3
B. BaCl2
C. (NH4)3PO3
Learning Goal Draw
the Lewis structures for
molecular compounds or
polyatomic ions.
D. Cu2CO3
E. N2O4
General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake
A molecule is
represented by a Lewis
structure in which the
valence electrons of all
the atoms are arranged
to give octets.
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General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake
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The Simplest Molecule, H2
Formation of H2 Molecule
A hydrogen molecule, H2,
• forms as the atoms move closer and the
positive charge of the nucleus attracts the
electron of the other atom.
• has a shared pair of electrons, a covalent
bond, to give a noble gas arrangement of He
to each H atom.
• forms when the molecule formed is more
stable than the two individual H atoms.
A covalent bond forms as H atoms move close
together to share electrons.
General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake
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General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake
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Lewis Structures, Molecules
Lewis Structures, Molecules
A molecule is represented by a Lewis structure in
which the valence electrons of all the atoms are
arranged to give octets.
• The shared electrons, or bonding pairs, are shown
as two dots or a single line between atoms.
• The nonbonding pairs, or lone pairs, are placed on
the outside of the atoms.
A molecule is represented by a Lewis structure in which the valence
electrons of all the atoms are arranged to give octets.
To draw the electron-dot formula for a fluorine molecule, F2,
• we start with the electron-dot symbols for each fluorine atom.
• each fluorine atom shares one electron to form a covalent bond,
giving each fluorine an octet.
General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake
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General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake
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Elements, Diatomic Molecules
Sharing Electrons Between Atoms of
Different Elements
The elements hydrogen, nitrogen, oxygen, fluorine, chlorine, bromine
and iodine exist as diatomic molecules.
The number of electrons a nonmetal atom shares and the number of
covalent bonds it forms are usually equal to the number of electrons
it needs to achieve a stable electron configuration.
Typical Bonding Patterns of Some Nonmetals
Core Chemistry Skill Drawing Lewis Structures
General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake
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Karen C. Timberlake
Drawing Lewis Structures
Molecules, Lewis Structures
To draw the electron-dot formula for
methane, CH4,
• draw the Lewis symbols for carbon and
hydrogen.
Electron-dot formulas for
common molecules such
as methane, ammonia,
and water are shown in
Table 6.13.
• carbon needs four hydrogen atoms to
have an octet.
• two bonding electrons between carbon
and hydrogen can be drawn as a line.
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• the central atom is the atom in the formula
with the least number of atoms.
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Karen C. Timberlake
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Guide to Drawing Electron-Dot Formulas
General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake
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Study Check
Draw the Lewis structure for PCl3, phosphorus
trichloride, which is used in the preparation of
pesticides and flame retardants.
General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake
© 2016 Pearson Education, Inc.
General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake
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Solution
Solution
Draw the Lewis structure for PCl3, phosphorus
trichloride, which is used in the preparation of
pesticides and flame retardants.
Draw the Lewis structure for PCl3, phosphorus trichloride,
which is used in the preparation of pesticides and flame
retardants.
STEP 1 Determine the arrangement of atoms.
In PCl3, P is the central atom; there is
only one phosphorus atom in the formula.
General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake
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STEP 2 Determine the total number of valence electrons.
Use the group number to determine the number of
valence electrons for each element.
General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake
© 2016 Pearson Education, Inc.
Solution
Solution
Draw the Lewis structure for PCl3, phosphorus
trichloride, which is used in the preparation of
pesticides and flame retardants.
Draw the Lewis structure for PCl3, phosphorus trichloride,
which is used in the preparation of pesticides and flame
retardants.
STEP 3 Attach each bonded atom to the
central atom with a pair of electrons.
Each bonding pair can be represented
with a single line.
General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake
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STEP 4 Place the remaining electrons using single or
multiple bonds to complete octets (two for H).
Six electrons (3 × 2 e−) are used to bond the central
P atom to three Cl atoms. Twenty valence electrons
are left.
General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake
Double and Triple Bonds
Exceptions to the Octet Rule
A double bond
• occurs when atoms share two pairs of electrons.
• forms when there are not enough electrons to
complete octets.
A triple bond
• occurs when atoms share three pairs of electrons.
• forms when there are not enough electrons to
complete octets.
While the octet rule is useful, there
are exceptions.
• Hydrogen requires just 2 electrons
to form a noble gas arrangement.
• Nonmetals P, S, Cl, Br, and I can
form compounds with 10 or 12
valence electrons.
• The S atom has an octet in many
compounds, but in SF6, there are
12 valence electrons or 6 bonds to
the sulfur atom.
General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake
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General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake
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6.7 Electronegativity and Bond Polarity
Electronegativity
The electronegativity
values of representative
elements in Group 1A
(1) to Group 7A (17).
The electronegativity of an atom is its ability to
attract the shared electrons in a bond. It
• increases from left to right going across a period
on the periodic table.
• increases from the bottom to the top of the
periodic table.
• is high for the nonmetals, with fluorine as the
highest.
• is low for the metals.
Learning Goal Use
electronegativity to
determine the polarity
of a bond.
Core Chemistry Skill Using Electronegativity
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Karen C. Timberlake
Electronegativity and the Periodic Table
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Karen C. Timberlake
Polarity of Bonds
The difference in
electronegativity of
bonding atoms can be
used to predict the
polarity of the bond.
In the H2 molecule,
electrons are shared
equally and the bond is
nonpolar. In the HCl
molecule, electrons are
shared unequally, and
the bond is polar.
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General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake
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General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake
Nonpolar Covalent Bonds
Polar Covalent Bonds
A nonpolar covalent bond occurs between nonmetals. It
• is an equal or almost equal sharing of electrons by the two
bonding atoms.
• has a very small electronegativity difference between atoms.
A polar covalent bond occurs between nonmetal atoms. It
• is an unequal sharing of electrons.
• has a moderate electronegativity difference.
Examples
Examples
Atoms
N-N
Cl-Br
H-Si
Electronegativity
Difference
3.0 − 3.0 = 0.0
3.0 − 2.8 = 0.2
2.1 − 1.8 = 0.3
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Type of Bond
Nonpolar covalent
Nonpolar covalent
Nonpolar covalent
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Atoms
O-Cl
Cl-C
O-S
Electronegativity
Difference
3.5 − 3.0 = 0.5
3.0 − 2.5 = 0.5
3.5 − 2.5 = 1.0
General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake
Type of Bond
Polar covalent
Polar covalent
Polar covalent
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Dipoles and Bond Polarity
Ionic Bonds
A polar covalent bond becomes more polar as the difference in
electronegativity increases. The separation of charges in a polar
bond is called a dipole.
The positive and negative ends of the dipole are located by using
• the lowercase Greek letter delta with a positive or negative
charge.
• an arrow that points from the positive to the negative end of
the dipole.
An ionic bond
• occurs between metal and nonmetal ions.
• is a result of electron transfer.
• has a large electronegativity difference (1.8 or more).
Examples
Atoms
Cl-K
N-Na
S-Cs
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Karen C. Timberlake
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Variations in Bonding
Electronegativity
Difference
3.0 – 0.8 = 2.2
3.0 – 0.9 = 2.1
2.5 – 0.7 = 1.8
Type of Bond
Ionic
Ionic
Ionic
General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake
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Electronegativity and Bond Types
The difference in electronegativity values for two
atoms can be used to predict the type of chemical
bond. If the electronegativity difference is
• between 0 and 0.4, the bond is nonpolar
covalent.
• between 0.5 and 1.8, the bond is polar covalent.
• greater than 1.8, the bond is ionic and the
electrons are considered transferred.
General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake
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Predicting Bond Type Using
Electronegativity
General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake
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Study Check
Use the electronegativity difference to identify
the type of bond (nonpolar covalent [NP], polar
covalent [P], or ionic [I]) between the following:
A. K—N
B. N—O
C. Cl—Cl
D. H—Cl
General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake
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General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake
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6.8 Shapes and Polarity of Molecules
VSEPR Theory
In a molecule of methane, CH4, the central C atom is
bonded to four H atoms. The best geometry for minimal
repulsion is tetrahedral, with bond angles of 109°.
Valence Shell Electron-Pair Repulsion Theory
(VSEPR)
• describes the orientation of electron groups around the
central atom.
• states that electron groups are arranged as far apart as
possible around the central atom.
• states that the specific shape of a molecule is
determined by the number of atoms attached to the
central atom.
Learning Goal Predict the three-dimensional structure
of a molecule, and classify it as polar or nonpolar.
General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake
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Core Chemistry Skill Predicting Shape
General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake
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Central Atoms with Two Electron Groups
Central Atoms with Three Electron Groups
In a molecule of CO2
• two electron groups are placed around the central atom, carbon.
• the repulsion is minimized by placing the two groups on opposite
sides of the carbon atom, giving this a linear arrangement with
bond angles of 180°.
• the shape with two electron groups around the central atom
is linear.
In a molecule of formaldehyde, H2CO3,
• three electron groups are placed around the central atom, carbon.
• the repulsion is minimized by placing the three groups as far apart
as possible at bond angles of 120°.
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Karen C. Timberlake
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• the shape with three electron groups around the central atom is
trigonal planar.
General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake
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Central Atoms with Three Electron Groups
Central Atoms with Four Electron Groups
In a molecule of SO2, there are three electron groups around the central
atom S:
1. a single-bonded O atom
2. a double-bonded O atom
3. a lone pair of electrons
• The repulsion is minimized by placing the three electron groups as far
apart as possible.
• The shape with two bonds and a lone pair on the central atom is bent
with a bond angle of 120°.
In a molecule of CH4
• four electron groups are attached to H atoms around the central
atom, carbon.
• the repulsion is minimized by placing the four electron groups at
corners of a tetrahedron with bond angles of 109°.
General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake
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• the shape with four bonds on the central atom is called
tetrahedral.
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Karen C. Timberlake
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Central Atoms with Four Electron Groups
Central Atoms with Four Electron Groups
In a molecule of NH3
• four electron groups, three bonds to H atoms and one lone pair,
are around the central atom, N.
• the repulsion is minimized by placing the four electron groups at
corners of a tetrahedron with bond angles of 109°.
In a molecule of H2O
• four electron groups, two bonds to H atoms and two lone pairs,
are around the central atom, O.
• the repulsion is minimized by placing the four electron groups at
corners of a tetrahedron with bond angles of 109°.
• the shape with three bonds and a lone pair on the central atom is
called trigonal pyrimidal.
• the shape with two bonds and two lone pairs on the central atom
is called bent.
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Karen C. Timberlake
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Molecular Shapes, Electron-Groups
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General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake
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Guide to Predicting Molecular Shape
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Karen C. Timberlake
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Predict Molecular Shape of H2S
Predict Molecular Shape of H2S
Predict the shape of a molecule of H2S.
Predict the shape of a molecule of H2S.
STEP 1 Draw the Lewis structure.
STEP 3 Use the atoms bonded to the
central atom to determine the shape.
The central atom S has two bonds
and two lone pairs. The shape is
bent, 109°.
STEP 2 Arrange electron groups around the
central atom to minimize repulsion.
To minimize repulsion, electron groups
have a tetrahedral arrangement.
General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake
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Karen C. Timberlake
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Study Check
Solution
State the number of electron groups and lone
pairs and use VSEPR theory to determine the
shape of the following molecules or ions as
tetrahedral, trigonal pyramidal, or bent.
State the number of electron groups and lone pairs and
use VSEPR theory to determine the shape of the
following molecules or ions as tetrahedral, trigonal
pyramidal, or bent.
A. PF3
STEP 1 Draw the Lewis structure.
B. H2O
C. CCl4
A. PF3
B. H2O
O
C. CCl4
H
H
General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake
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General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake
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Solution
Solution
State the number of electron groups and lone pairs and use
VSEPR theory to determine the shape of the following
molecules or ions as tetrahedral, trigonal pyramidal, or bent.
State the number of electron groups and lone pairs and use
VSEPR theory to determine the shape of the following
molecules or ions as tetrahedral, trigonal pyramidal, or bent.
STEP 2 Arrange electron groups around the central
atom to minimize repulsion.
A. PF3: To minimize repulsion, the electron groups
would have a tetrahedral arrangement.
B. H2O: To minimize repulsion, the electron groups
would have a tetrahedral arrangement.
C. CCl4: To minimize repulsion, the electron groups
would have a tetrahedral arrangement.
STEP 3 Use the atoms bonded to the central atom to
determine the molecular shape.
A. PF3: With three bonds and one lone pair on the
central atom, the shape is trigonal pyrimidal.
B. H2O: With two bonds and two lone pairs on the
central atom, the shape is bent.
C. CCl4: With four bonds on the central atom, the
shape is tetrahedral.
General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake
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General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake
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Polarity of Molecules
Polarity of Molecules
Nonpolar molecules
• such as H2, Cl2, and O2 are nonpolar because they contain
nonpolar bonds.
Polar molecules such as HCl are polar because
• one end of the molecule is more negatively charged than
the other.
• the polar bonds in the molecule do not cancel each other.
• the electrons are shared unequally in the polar covalent bond.
• with polar bonds can be nonpolar if the polar bonds (dipoles)
cancel in a symmetrical arrangement, such as in CO2 and CF4.
Core Chemistry Skill Identifying Polarity of Molecules
General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake
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Polarity of Molecules
Polarity of Molecules
In a polar molecule such as H2O, there
• are two lone pairs and two bonds around the central atom.
• are dipoles that do not cancel since the shape is bent,
making the molecule positive at one end and negative at
the other end.
• is a partial negative charge on the central atom.
In a polar molecule such as NH3, there
• is one lone pair and three bonds around the central atom.
• are dipoles that do not cancel since the shape is trigonal
pyramidal, making the molecule positive at one end and
negative at the other end.
• is a partial negative charge on the central atom.
General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake
© 2016 Pearson Education, Inc.
Guide to Determining the Polarity of a
Molecule
© 2016 Pearson Education, Inc.
General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake
Determination of Polarity
Determine if the molecule OF2 is polar or nonpolar.
STEP 1 Determine if the bonds are polar covalent
or nonpolar covalent.
O (3.5) and F (4.0) give an electronegativity
difference of 0.5, which makes the bonds
polar covalent.
STEP 2 If the bonds are polar covalent, draw the
Lewis structure and determine if the
dipoles cancel.
OF2 is a polar molecule.
General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake
© 2016 Pearson Education, Inc.
O
F
F
© 2016 Pearson Education, Inc.
General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake
Study Check
Solution
Identify each of the following molecules as
polar or nonpolar.
A. PBr3
B. HBr
Identify each of the following molecules as polar or nonpolar.
STEP 1
STEP 2
Bonds, polar or
Draw molecule to see if
nonpolar
any polar bonds cancel
A. PBr3 P = 2.1
P
Br = 2.8, polar
polar Br
Br
Br
C. CH4
B. HBr H = 2.1
Br = 2.8, polar
polar H Br
C. CH4 C = 2.5
H = 2.1, nonpolar
nonpolar
H
C
H
General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake
© 2016 Pearson Education, Inc.
General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake
H
H
© 2016 Pearson Education, Inc.
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10/12/2015
6.9 Attractive Forces in Compounds
Dipole-Dipole, Hydrogen Bonds
The protein shape is
stabilized by attractive forces
between functional groups of
side chains (R groups) on
the amino acids, causing it to
twist and bend into a specific
three-dimensional shape.
In covalent compounds, polar molecules
• exert attractive forces called dipole-dipole attractions.
• form strong dipole attractions called hydrogen bonds
between hydrogen atoms bonded to F, O, or N, and a lone pair on
F, O, or N.
Hydrogen bonds are the strongest force between molecules and play
a major role in the shape of DNA.
Learning Goal Describe the
attractive forces between
ions, polar covalent
molecules, and nonpolar
covalent molecules.
Core Chemistry Skill Identifying Attractive Forces
General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake
© 2016 Pearson Education, Inc.
General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake
© 2016 Pearson Education, Inc.
Dispersion Forces
Melting Points and Attractive Forces
Dispersion forces are
• weak attractions between nonpolar molecules.
• caused by temporary dipoles that develop when molecules
bump into each other.
• weak but make it possible for nonpolar molecules to form
liquids and solids.
Melting points of compounds
• are related to the strength of attractive forces
between molecules or compounds.
• are lower due to weak forces such as
dispersion forces.
• are higher due to stronger attractive forces such as
hydrogen bonding.
• are highest in ionic compounds due to the strong
attractive forces between ions in the compound.
General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake
© 2016 Pearson Education, Inc.
Melting Points and Attractive Forces
General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake
© 2016 Pearson Education, Inc.
General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake
© 2016 Pearson Education, Inc.
Comparison of Bonding and
Attractive Forces
General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake
© 2016 Pearson Education, Inc.
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10/12/2015
Study Check
Chemistry Link to Health: Attractive Forces,
Proteins
Identify the main type of attractive forces that are
present in liquids of the following compounds:
ionic bonds, dipole-dipole, hydrogen bonds, or
dispersion forces.
A. NCl3
B. H2O
C. Br-Br
D. KCl
E. NH3
General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake
© 2016 Pearson Education, Inc.
Proteins are biological molecules with many
different functions. They are needed for
• structural components such as cartilage,
muscles, hair.
• the formation of enzymes that regulate
biological reactions.
• myoglobin and hemoglobin, which transport
oxygen in blood and muscle.
© 2016 Pearson Education, Inc.
General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake
Chemistry Link to Health: Attractive Forces,
Proteins
Chemistry Link to Health: Attractive Forces,
Proteins
Proteins are composed of building blocks called amino acids. Every
amino acid has a central carbon atom bonded to
• an –NH3+, from an amine.
• a –COO−, from a carboxylic acid.
• an H atom.
• an R group, which is unique for each amino acid.
Several amino acids have R
groups or side chains that contain
• an amide group, –CONH2.
• a hydroxyl, – OH, group.
• a carboxyl, –COOH, group
ionized as carboxylate, –COO−.
• an amine, –NH2, group ionized
as ammonium, –NH3+.
General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake
© 2016 Pearson Education, Inc.
General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake
© 2016 Pearson Education, Inc.
Chemistry Link to Health: Attractive Forces,
Proteins
Chemistry Link to Health: Attractive Forces,
Proteins
The primary structure of a protein is its sequence of amino
acids. It is the sequence of amino acids that determines the
protein’s function.
Proteins have a higher
level of structure that is
determined by the
attractive forces between
the amino acids.
Amino acids in a protein are linked by a peptide bond
between the COO− of one amino acid and the –NH3+ of the
next amino acid.
General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake
© 2016 Pearson Education, Inc.
When hydrogen bonds
form between a hydrogen
atom in an N—H group and
the oxygen of the C═O
group, the protein forms an
alpha helix.
General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake
H-bonds can form between the –OH of
serine and the –NH2 of asparagine.
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10/12/2015
Chemistry Link to Health: Attractive Forces,
Proteins
Hydrogen bonds can
also form between
the polar side chains
of the amino acids
on the outside of the
protein and the –OH
and –H of polar
water molecules in
the external aqueous
environment.
General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake
Concept Map
Attractive forces hold the protein in a
specific shape.
© 2016 Pearson Education, Inc.
General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake
© 2016 Pearson Education, Inc.
28