chemistry: matter and change ch. 5-8 resources · study guide chemistry: matter and change •...

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100 Chemistry: Matter and Change • Chapter 8 Study Guide

Covalent BondingCovalent Bonding

Section 8.1 The Covalent BondIn your textbook, read about the nature of covalent bonds.

Use each of the terms below just once to complete the passage.

When sharing of electrons occurs, the attachment between atoms that results is called

a(n) (1) . When such an attachment is formed, bond dissociation

energy is released, and the process is (2) . When two or more

atoms bond by means of electron sharing, the resulting particle is called a(n)

(3) . If the electrons shared are centered between the two atoms, the

attachment is called a(n) (4) . If the sharing involves the overlap of

parallel orbitals, the attachment is called a(n) (5) .

In your textbook, read about single and multiple bonds and bond strength.

Circle the letter of the choice that best completes the statement or answers the question.

6. In what form do elements such as hydrogen, nitrogen, and oxygen normally occur?

a. as single atoms c. as molecules containing three atoms

b. as molecules containing two atoms d. as molecules containing four atoms

7. How many electrons are shared in a double covalent bond?

a. none b. one c. two d. four

8. Bond length is the distance between

a. two molecules of the same substance. c. the nuclei of two attached atoms.

b. the electrons in two attached atoms. d. the orbitals of two attached atoms.

9. Which of the following relationships relating to bond length is generally correct?

a. the shorter the bond, the stronger the bond

b. the shorter the bond, the weaker the bond

c. the shorter the bond, the fewer the electrons in it

d. the shorter the bond, the lower the bond dissociation energy

STUDY GUIDECHAPTER 8

covalent bond molecule sigma bond exothermic pi bond

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Study Guide Chemistry: Matter and Change • Chapter 8 101

Section 8.2 Naming MoleculesIn your textbook, read about how binary compounds and acids are named from theirformulas.

For each statement below, write true or false.

1. Binary molecular compounds are generally composed of a metal and anonmetal.

2. The second element in the formula of a binary compound is named usingthe suffix -ite.

3. The prefix tetra- indicates three atoms.

4. The prefix hexa- indicates six atoms.

5. In naming the first element in a formula, the prefix mono- is not used.

6. For binary acids, the hydrogen part of the compound is named using theprefix hydro-.

7. An oxyacid contains only two elements.

8. If the name of the anion of an oxyacid ends in -ate, the acid namecontains the suffix -ous.

In your textbook, read about naming molecular compounds and oxyacids.

For each item in Column A, write the letter of the matching item in Column B.

Column A Column B

9. CO

10. CO2

11. H2CO3

12. NH3

13. N2O4

14. HNO2

15. HNO3

16. HBr

17. HBrO3


a. hydrobromic acid

b. dinitrogen tetroxide

c. carbon monoxide

d. nitrous acid

e. ammonia

f. nitric acid

g. carbonic acid

h. bromic acid

i. carbon dioxide

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Section 8.3 Molecular StructuresIn your textbook, read about Lewis structures.


1. A structural formula shows the arrangement of the atoms in a molecule.

2. The central atom in a molecule is the one with the highest electronaffinity.

3. In molecules, hydrogen is always a terminal atom.

4. The number of bonding pairs in a molecule is equal to the number ofelectrons.

5. To find the total number of electrons available for bonding in a positiveion, you should add the ion charge to the total number of valenceelectrons of the atoms present.

6. The electrons in a coordinate covalent bond are donated by both thebonded atoms.

7. Resonance occurs when more than one valid Lewis structure can bewritten for a molecule.

8. Nitrate is an example of an ion that forms resonance structures.

9. The carbon dioxide molecule contains two double bonds.

10. All electrons in an atom are available for bonding.

11. In the sulfate ion (SO42�), 32 electrons are available for bonding.

12. When carbon and oxygen bond, the molecule contains ten pairs ofbonding electrons.

In your textbook, read about resonance structures and exceptions to the octet rule.

For each item in Column A, write the letter of the matching item in Column B.

Column A Column B

13. Odd number of valence electrons

14. Fewer than 8 electrons around an atom

15. More than 8 electrons around central atom

16. More than one valid Lewis structure


a. O3

b. BF3

c. NO

d. SF6

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Section 8.4 Molecular ShapeIn your textbook, read about the VSEPR model.

Circle the letter of the choice that best completes the statement.

1. The VSEPR model is used mainly to

a. determine molecular shape. c. determine ionic charge.

b. write resonance structures. d. measure intermolecular distances.

2. The bond angle is the angle between

a. the sigma and pi bonds in a double bond. c. two terminal atoms and the central atom.

b. the nucleus and the bonding electrons. d. the orbitals of a bonding atom.

3. The VSEPR model is based on the idea that

a. there is always an octet of electrons around an atom in a molecule.

b. electrons are attracted to the nucleus.

c. molecules repel one another.

d. shared and unshared electron pairs repel each other as much as possible.

4. The shape of a molecule whose central atom has four pairs of bonding electrons is

a. tetrahedral. b. trigonal planar. c. trigonal pyramidal. d. linear.

5. The shape of a molecule that has two covalent single bonds and no lone pairs on the central atom is


6. The shape of a molecule that has three single covalent bonds and one lone pair on thecentral atom is


In your textbook, read about hybridization.

Use each of the terms below just once to complete the passage.

The formation of new orbitals from a combination or rearrangement of valence electrons

is called (7) . The orbitals that are produced in this way are

(8) to one another. An example of an element that commonly

undergoes such formation is (9) . When this atom combines its three

p orbitals and its one s orbital, the orbitals that result are called (10)

orbitals. An example of a molecule that has this type of orbital is (11) .


carbon hybridization sp3 identical methane

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Section 8.5 Electronegativity and PolarityIn your textbook, read about electronegativity.

Use the table of electronegativities below to answer the following questions.

1. What is the meaning of the term electronegativity?

2. Which element has the highest electronegativity? What is the numerical value? What are thename and group number of the chemical family that has the highest overall electronegativities?

3. Which element has the lowest electronegativity? What is the numerical value? What are thename and group number of the chemical family that has the lowest overall electronegativities?

4. What general trend in electronegativity do you note going down a group? Across a period?

5. How are the electronegativity values used to determine the type of bond that existsbetween two atoms?

In your textbook, read about the properties of covalent compounds.


6. Ionic compounds are usually soluble in polar substances.

7. In a covalent molecular compound, the attraction between molecules tendsto be strong.

Electronegativities of Some Elements

MetalMetalloidNonmetal

78Pt2.2

79Au2.4

80Hg1.9

81Tl1.8

82Pb1.8

83Bi1.9

85At2.2

28Ni

1.91

29Cu

1.90

30Zn

1.65

31Ga

1.81

32Ge

2.01

33As

2.18

34Se

2.55

35Br

2.96

46Pd

2.20

47Ag

1.93

48Cd

1.69

49In

1.78

50Sn

1.96

51Sb

2.05

52Te2.1

53I

2.66

13Al

1.61

14Si

1.90

15P

2.19

16S

2.58

17Cl

3.16

5B

2.04

6C

2.55

7N

3.04

8O

3.44

9F

3.98

84Po2.0

1H

2.203Li

0.98

11Na

0.9319K

0.82

37Rb

0.82

55Cs

0.7987Fr0.7

88Ra0.9

89Ac1.1

56Ba

0.89

57La

1.10

72Hf1.3

73Ta1.5

74W1.7

75Re1.9

76Os2.2

77Ir

2.2

38Sr

0.95

39Y

1.22

40Zr

1.33

41Nb1.6

42Mo2.16

20Ca

1.00

21Sc

1.36

22Ti

1.54

23V

1.63

24Cr

1.66

43Tc

2.10

44Ru2.2

25Mn1.55

26Fe

1.83

27Co

1.88

45Rh

2.28

12Mg1.31

4Be

1.57


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In your textbook, read about bond polarity.

Using the table of electronegativities on the preceding page, circle the letter of the choicethat best completes the statement or answers the question.

8. Unequal sharing of electrons between two bonded atoms always indicates

a. a nonpolar covalent bond. c. a polar covalent bond.

b. an ionic bond. d. a polar molecule.

9. When electronegativities of two bonded atoms differ greatly, the bond is

a. polar covalent. b. coordinate covalent. c. polar covalent. d. ionic.

10. What is the electronegativity difference that usually is the dividing line between covalentand ionic bonds?

a. 1.0 b. 1.7 c. 2.7 d. 4.0

11. The symbol �� is placed next to which of the following?

a. the less electronegative atom in a polar covalent bond c. a positive ion

b. the more electronegative atom in a polar covalent bond d. the nucleus

12. A nonpolar covalent bond is one in which

a. electrons are transferred. c. electrons are shared equally.

b. electrons are shared unequally. d. both electrons are provided by the same atom.

13. Molecules containing only polar covalent bonds

a. are always polar. c. are always ionic.

b. may or may not be polar. d. are always nonpolar.

14. What factor other than electronegativity determines whether a molecule as a whole ispolar or not?

a. temperature b. its geometry c. its physical state d. its mass

15. Which of the following correctly describes the compound water, H2O?

a. ionic c. polar overall, with nonpolar covalent bonds

b. nonpolar overall, with polar covalent bonds d. polar overall, with polar covalent bonds

16. Which of the following correctly describes the compound carbon tetrachloride, CCl4?

a. ionic c. polar overall, with nonpolar covalent bonds

b. nonpolar overall, with polar covalent bonds d. polar overall, with polar covalent bonds

17. A molecule of ammonia, NH3, is

a. nonpolar because it is linear.

b. polar because it is linear.

c. nonpolar because there is no electronegativity difference.

d. polar because there is an electronegativity difference and the molecule is trigonal pyramidal.


Section 8.5 continued

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106 Chemistry: Matter and Change • Chapter 8 Chapter Assessment

Covalent BondingCovalent Bonding

Reviewing VocabularyMatch the definition in Column A with the term in Column B.

Column A Column B

1. The tendency of an atom in a compound to attractelectrons

2. A kind of bond in which there is unequal sharing ofelectrons

3. Any bond in which there is electron sharing

4. The particle formed when two or more atoms bondcovalently

5. Reactions that occur when more energy is releasedforming new bonds than is required to break bonds in theinitial reactants

6. A kind of bond in which electrons are shared in an areacentered between the two atoms

7. A kind of bond formed by overlap of parallel orbitals

8. Any acidic compound that contains oxygen

9. A model that shows how the atoms are arranged in amolecule

10. Reactions that occur when more energy is required tobreak existing bonds in reactants than is released whennew bonds form in the product molecules

11. A condition that occurs when more than one valid Lewisstructure can be drawn for a molecule

12. A kind of bond in which one of the atoms provides bothelectrons for sharing

13. A model used to determine molecular shape

14. The combining of orbitals in an atom to form new,identical orbitals

CHAPTER ASSESSMENTCHAPTER 8

a. structural formula

b. molecule

c. VSEPR model

d. coordinate covalent bond

e. hybridization

f. oxyacid

g. electronegativity

h. sigma bond

i. polar covalent

j. pi bond

k. covalent bond

l. resonance

m. endothermic

n. exothermic

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Chapter Assessment Chemistry: Matter and Change • Chapter 8 107

Understanding Main Ideas (Part A)

Circle the letter of the choice that best completes the statement or answers the question.

1. In the formation of a covalent bond, electrons are

a. shared. b. lost. c. gained. d. transferred.

2. Which of the following elements normally exists in the form of diatomic molecules?

a. helium b. argon c. iron d. nitrogen

3. Four electrons are shared in a

a. single covalent bond. c. triple covalent bond.

b. double covalent bond. d. quadruple covalent bond.

4. Which of the following molecules contains only sigma bonds?

a. methane b. oxygen c. carbon dioxide d. nitrogen

5. Which of the following molecules contains a triple bond?

a. methane b. oxygen c. carbon dioxide d. nitrogen

6. How many pi bonds are there in a triple bond?

a. none b. one c. two d. three

7. Which of the following molecules would be expected to have the greatest bond dissociation energy?

a. F2 b. O2 c. N2 d. Cl2

In the space at the left, write true if the statement is true; if the statement is false,change the italicized term to make it true.

8. In a chemical name, the prefix used to indicate the presence oftwo atoms of a given kind is bi-.

9. The prefix hydro- is used in naming binary acids.

10. The oxyacid suffix for an acid that contains an anion ending in -ate is -ic.

11. In Lewis structures, hydrogen is always a terminal atom.

12. In the carbon dioxide molecule, the central atom is a carbon atom.

13. In the compound BH3, the boron atom has more than an octet ofelectrons.

14. The VSEPR model is based on the idea that in a molecule, nucleirepel each other as much as possible.


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Understanding Main Ideas (Part B)

The diagram below represents different hybridizations of the orbitals of three carbonatoms, labeled X, Y, and Z. Use the diagram to answer the questions that follow.

1. Write the electron configuration of an unbonded carbon atom (atomic number 6) beforehybridization occurs.

2. Look at carbon atom X in the diagram. What is the symbol for the hybrid orbitals formedby carbon atom X? How many of them are there in that atom?

3. Does carbon atom X have any unhybridized orbitals? If so, tell how many and write thesymbol for them.

4. To how many other atoms would carbon atom X be attached? What types of bonds—single, double, or triple—would they be? State whether each attachment would involvesigma bonds, pi bonds, or both.

5. What would be the shape of the molecule formed by carbon atom X when it bonds inthat way?

6. Suppose that the attachments in that molecule are to atoms of the same kind with an electronegativity greater than that of carbon. Would each bond be polar or nonpolar?Would the molecule as a whole be polar or nonpolar? Explain.

7. Look at carbon atom Y in the diagram. What is the symbol for the hybrid orbitals formedby carbon atom Y? How many of them are there in that atom?

sp3

hybridsp3

hybrid

sp3

hybridsp2

hybrid

sp2

hybrid

sp2

hybridsphybrid

sphybrid

p orbital(above andbelow)

p orbital(above andbelow)

p orbital(above and

below)

sp3 hybrid

CC C

X Y Z


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Thinking CriticallyThe graph shows the electronegativities of the elements of periods 2 and 3 of the periodictable, except for the noble gases. Use the graph to answer the following questions.

1. If two atoms of differing electronegativity are bonded covalently to each other, what istrue of the electrons they share? What type of bond results in such a case?

2. How does the electronegativity of boron (B) compare with that of nitrogen (N)? In termsof the periodic table, how are these two elements related? Compare aluminum (Al) withphosphorus (P) in the same way.

3. Describe the trend in electronegativity illustrated for period-2 and period-3 elements.

4. How does the electronegativity of boron (B) compare with that of aluminum (Al)? Interms of the periodic table, how are these two elements related? Compare nitrogen (N)with phosphorus (P) in the same way.

5. Describe the trend in electronegativity within a group of the periodic table, as suggestedby the graph.

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

1 2 13 14 15 16 17Group number

Elec

tro

neg

ativ

ity

Li

Be

B

C

N

O

F

Na

MgAl

SiP

S

ClPeriod 2

Period 3


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Applying Scientific MethodsA college chemistry student is studying the properties of four unknown compounds, W, X, Y,and Z. She has been informed that one of them is ionic and that the other three are covalent.Of the latter, she has been told that the attractions between the formula units are dispersionforces in one case, hydrogen bonds in another, and covalent (network) bonds in another. Shehas been asked to determine the type of attractions for each substance. In an attempt to do so,she carries out experiments that reveal information about the substances’ properties. Use thisinformation to answer the questions that follow.

1. On the basis of the results of her hardness test, the student concludes that unknowns Wand X are covalent substances, and that either Y or Z is the ionic substance. Comment onthe soundness of her conclusion, given only the hardness information.

2. The student examines the melting-point data, but claims that it is not useful in determiningthe substances’ types of attractions. How would you reply to that claim?

3. On the basis of the results of the boiling-point and melting-point tests, the student concludes that W is the hydrogen-bonded substance and that X must therefore be thesubstance that has the dispersion forces. Is that conclusion valid? Explain.


Property Unknown W Unknown X Unknown Y Unknown Z

Hardness of solid soft soft brittle brittle

Melting point (°C) �10 �200 1500 3000

Boiling point (°C) 120 �150 2500 4500

Solubility in polar solvent very soluble insoluble very soluble insoluble

Solubility in nonpolar solvent insoluble very soluble insoluble insoluble

Conductivity of solid nonconducting nonconducting nonconducting nonconducting

Conductivity of liquid nonconducting nonconducting conducting nonconducting

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4. On the basis of the results of her solubility test, the student concludes that X must becovalent. Comment, and state any further conclusions that can be derived about the othersubstances.

5. On the basis of her electrical conductivity test, the student states that there must be someerror because unknown Y acts like a covalent substance when solid but like an ionic sub-stance when melted. Comment on her statement.

6. The student examines the entire set of data but is unable to come to final, definite con-clusions about the substances’ types of attractions. Is it possible to do so, given the data?Explain, and state your own conclusions if any.

7. How do the overall procedure and your reasoning illustrate scientific methods?

Applying Scientific Methods, continued


chemistry: matter and change ch. 5-8 resources · study guide chemistry: matter and change •...

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