05 CTR ch08 7/12/04 8:12 AM Page 181 MOLECULAR...

Chapter 8 Covalent Bonding 181

Section Review

Objectives• Distinguish molecular compounds from ionic compounds

• Identify the information a molecular formula provides

Vocabulary

Part A CompletionUse this completion exercise to check your understanding of the concepts and termsthat are introduced in this section. Each blank can be completed with a term, shortphrase, or number.

Every substance is either an element or a(n) . 1.

A compound is either or ionic in nature. Most molecular 2.

compounds are composed of two or more . Molecules 3.

consisting of two atoms are molecules. The chemical 4.

formula of a molecular compound is a . Molecular 5.

compounds tend to have melting and boiling points, while 6.

ionic compounds tend to have melting and boiling points. 7.

A molecular formula shows how many of each 8.

element a molecule contains, but it does not indicate the 9.

of the molecule.

Part B True-FalseClassify each of these statements as always true, AT; sometimes true, ST; or never true, NT.

________ 10. A diatomic molecule contains two or three atoms.

________ 11. Molecular compounds have relatively high boiling points.

9

8

7

6

5

4

3

2

1

• covalent bond

• molecule

• diatomic molecule

• molecular compound

• molecular formula

Name ___________________________ Date ___________________ Class __________________

MOLECULAR COMPOUNDS8.1

© Pe

arson

Educ

ation

, Inc

., pu

blish

ing as

Pears

on Pr

entic

e Hall

. All r

ights

reserv

ed.

05_CTR_ch08 7/12/04 8:12 AM 81

182 Core Teaching Resources

________ 12. The molecular structure of carbon dioxide is one carbon atom withtwo oxygen atoms on opposite sides of it.

________ 13. Covalent bonds exist when combining atoms give up or accept electrons.

________ 14. A molecule contains two atoms.

Part C MatchingMatch each description in Column B to the correct term in Column A.

Part D Questions and ProblemsAnswer the following in the space provided.

20. A compound has a boiling point of 40°C. Is this compound most likely an ionicor a molecular compound?

21. Identify the number and kinds of atoms present in a molecule of eachcompound.

a. butane (C4H10)

b. fluorobenzene (C6H5F)

22. Classify each particle as an atom or a molecule.

a. CH4 d. He

b. Ne e. CO2

c. O2

Column B

a. compound composed of molecules

b. a molecule consisting of two atoms

c. shows the kinds and numbers present in a molecule ofa compound

d. joins atoms held together by sharing electrons

e. an electrically neutral group of atoms joined togetherby covalent bonds

Column A

molecule

molecular compound

covalent bond

diatomic molecule

molecular formula

________ 15.

________ 16.

________ 17.

________ 18.

________ 19.

Name ___________________________ Date ___________________ Class __________________©

Pearson Education, Inc., publishing as Pearson Prentice Hall. All rights reserved.

05_CTR_ch08 7/12/04 8:12 AM Page 182


Section Review

Objectives• State a rule that usually tells how many electrons are shared to form a covalent bond

• Describe how electron dot formulas are used

• Predict when two atoms are likely to be joined by a double or a triple covalent bond

• Distinguish between a single covalent bond and other covalent bonds

• Describe how the strength of a covalent bond is related to its bond dissociation energy

• Describe how resonance structures explain bonding

• Identify some exceptions to the octet rule

Vocabulary

Part A CompletionUse this completion exercise to check your understanding of the concepts and terms that areintroduced in this section. Each blank can be completed with a term, short phrase, or number.

When atoms share electrons to gain the configuration 1.

of a noble gas, the bonds formed are . A pair of 2.

valence electrons constitutes a covalent bond. Pairs of 3.

valence electrons that are not shared between atoms are called 4.

. Sometimes two or three pairs of electrons may be shared 5.

to give covalent bonds. In some cases, only one of the 6.

atoms in a bond provides the pair of bonding electrons; this is a 7.

. is required to break covalent bonds between 8.

atoms. The total energy required to break the bond between two 9.

covalently bonded atoms is known as the . 10.

When it is possible to write two or more valid electron dot

formulas for a molecule or ion, each formula is referred to as a .10

9

87

6

5

4

32

1

• single covalent bond

• structural formulas

• unshared pairs

• double covalent bonds

• triple covalent bonds

• coordinate covalent bond

• polyatomic ion

• bond dissociation energy

• resonance structures

Name ___________________________ Date ___________________ Class __________________

THE NATURE OF COVALENT BONDING8.2

© Pe

arson

Educ

ation

, Inc

., pu

blish

ing as

Pears

on Pr

entic

e Hall

. All r

ights

reserv

ed.

05_CTR_ch08 7/12/04 8:12 AM Page 183



________ 11. The modern interpretation of resonance is that electron pairs rapidly flipback and forth between the various electron dot structures.

________ 12. The compound NH3 contains two double covalent bonds.

________ 13. The chemical formulas of molecular compounds show the number andtype of atoms in each molecule.

________ 14. A molecule of bromine has six unshared pairs of electrons.

________ 15. Carbon forms four single covalent bonds with other atoms.

________ 16. A bond in which one atom contributes both bonding electrons is called apolyatomic covalent bond.



22. Draw electron dot structures for each of the following compounds

a. Br2

b. HCN

c. NH4�

Column B

a. a chemical formula that shows the arrangement ofatoms in a molecule or a polyatomic ion

b. the amount of energy required to break a covalent bondbetween atoms

c. a tightly bound group of atoms that has a positive ornegative charge and behaves as a unit

d. a covalent bond in which one atom contributes bothbonding electrons

e. a chemical bond in which only one pair of electrons isshared by two bonded atoms

Column A

________ 17. single covalent bond

________ 18. structural formula

________ 19. bond dissociationenergy

________ 20. polyatomic ion

________ 21. coordinate covalentbond

Name ___________________________ Date ___________________ Class __________________©


05_CTR_ch08 7/12/04 8:12 AM Page 184


Section Review

Objectives• Identify the difference between atomic and molecular orbits

• Describe how VSEPR theory helps predict the shapes of molecules

• Identify the ways in which orbital hybridization is useful in describing molecules

Vocabulary


The quantum mechanical model of bonding assumes that 1.

atomic orbitals overlap to produce . A molecular orbit that 2.

can be occupied by two electrons of a covalent bond is called a 3.

, whose energy is than that of the atomic orbitals 4.

from which it formed. When two atomic orbitals combine to form 5.

a molecular orbital that is symmetrical around the axis connecting 6.

two atomic nuclei, a bond is formed. When atomic 7.

orbitals overlap side by side, they produce bonds. 8.

Electron dot structures fail to reflect the shapes

of molecules. states that because electron pairs repel,

molecular shape adjusts so the valence-electron pairs are as

far apart as possible. Another way to describe molecules that

provides information about both molecular bonding and

molecular shape is .8

7

6

5

4

32

1

• molecular orbitals

• bonding orbital

• sigma bond

• pi bond

• tetrahedral angle

• VSEPR theory

• hybridization

Name ___________________________ Date ___________________ Class __________________

BONDING THEORIES8.3

© Pe

arson

Educ

ation

, Inc

., pu

blish

ing as

Pears

on Pr

entic

e Hall

. All r

ights

reserv

ed.

05_CTR_ch08 7/12/04 8:12 AM Page 185



________ 9. Unshared pairs of electrons affect the shape of molecules.

________ 10. Molecular orbitals involve pi bonding.

________ 11. A bonding orbital is a molecular orbital whose energy is higher than thatof the atomic orbitals from which it is formed.

________ 12. With hybridization, several atomic orbitals overlap to form the same totalnumber of equivalent hybrid orbitals.

________ 13. Sigma and pi bonds are found in the same molecule.

________ 14. The methane molecule has four orbitals with tetrahedral angles of 109.5°.



20. Indicate the hybrid orbitals used by each carbon atom in the followingcompound.

H3C 2 C 3 C 2 C 4 C 2 CH3

H

2

H

2

Column B

a. states that because electron pairs repel, molecules adjust theirshapes so that valence-electron pairs are as far apart as possible

b. a process in which several atomic orbitals overlap to form thesame number of equivalent hybrid orbitals

c. a term used to describe the shape of certain molecules such asCO2

d. a bond formed when two atomic orbitals combine to form amolecular orbital that is symmetrical along the axis connectingthe two atomic nuclei

e. a bond in which the bonding electrons are most likely to befound in the sausage-shaped regions above and below thenuclei of the bonded atoms

Column A

________ 15. sigma bond

________ 16. pi bond

________ 17. VSEPR theory

________ 18. hybridization

________ 19. linear molecule

Name ___________________________ Date ___________________ Class __________________©


05_CTR_ch08 7/12/04 8:12 AM Page 186


Section Review

Objectives• Describe how electronegativity values determine the charge distribution in a polar

bond

• Describe what happens to polar molecules when placed between oppositelycharged metal plates

• Distinguish intermolecular attractions from ionic bonds and from covalent bonds

• Identify the reason network solids have high melting points or decomposewithout melting

Vocabulary


When like atoms are joined by a covalent bond, the bonding 1.

electrons are shared , and the bond is . When the 2.

atoms in a bond are not the same, the bonding electrons are shared 3.

, and the bond is . The degree of polarity of a bond 4.

between any two atoms is determined by consulting a table of 5.

. The attractions between opposite poles of polar molecules 6.

are called . Another strong intermolecular attractive force 7.

is the , in which a hydrogen covalently bonded to a very 8.

atom, such as , is also weakly bonded to an 9.

unshared electron pair of another electronegative atom.

98

7

6

5

43

21

• nonpolar covalent bond

• polar covalent bond

• polar bond

• polar molecule

• dipole

• van der Waals forces

• dipole interactions

• dispersion forces

• hydrogen bonds

• network solids

Name ___________________________ Date ___________________ Class __________________

POLAR BONDS AND MOLECULES8.4

© Pe

arson

Educ

ation

, Inc

., pu

blish

ing as

Pears

on Pr

entic

e Hall

. All r

ights

reserv

ed.

05_CTR_ch08 7/12/04 8:12 AM Page 187



________ 10. In a polar covalent bond, the more electronegative atom has a slightpositive charge.

________ 11. In general, the electronegativity values of nonmetallic elements aregreater than the electronegativity values of metallic elements.

________ 12. A molecule with polar bonds is dipolar.

________ 13. Covalent compounds are network solids.

________ 14. If the electronegativity difference between two atoms is greater than 2.0,they will form an ionic bond.

________ 15. Dispersion forces are weaker than hydrogen bonds.


Column B

a. a substance in which all of the atoms are covalentlybonded to each other

b. a bond formed when the atoms in a molecule are alikeand the bonding electrons are shared equally

c. a term used to describe the weakest intermolecularattractions; these include dispersion forces and dipoleinteractions

d. a bond formed when two different atoms are joined by acovalent bond and the bonding electrons are sharedunequally

e. a molecule in which one end is slightly positive and theother end is slightly negative

Column A

________ 16. nonpolar covalentbond

________ 17. polar covalent bond

________ 18. polar molecule

________ 19. van der Waals forces

________ 20. network solid

Name ___________________________ Date ___________________ Class __________________©


05_CTR_ch08 7/12/04 8:12 AM Page 188



21. Arrange the following intermolecular attractions in order of increasing strength:dipole interactions, dispersion forces, and hydrogen bonds.

22. State whether the following compounds contain polar covalent bonds, non-polar covalent bonds, or ionic bonds, based on their electronegativities.

a. KF a.

b. SO2 b.

c. NO2 c.

d. Cl2 d.

Name ___________________________ Date ___________________ Class __________________©

Pears

on Ed

ucati

on, I

nc.,

publi

shing

as Pe

arson

Pren

tice H

all. A

ll righ

ts res

erved

.

05_CTR_ch08 7/12/04 8:12 AM Page 189


Practice ProblemsIn your notebook, solve the following problems.

SECTION 8.1 MOLECULAR COMPOUNDS1. Classify each of the following as an atom or a molecule.

a. Be c. N2 e. Ne

b. CO2 d. H2O

2. Which of the following are diatomic molecules?

a. CO2 c. O2 e. CO

b. N2 d. H2O

3. What types of elements tend to combine to form molecularcompounds?

4. What information does a molecule’s molecular structure give?

5. How do ionic compounds and molecular compounds differ in theirrelative melting and boiling points?

SECTION 8.2 THE NATURE OF COVALENT BONDING1. Draw the electron dot structure for hydrogen fluoride, HF.

2. Draw the electron dot structure for phosphorus trifluoride, PF3.

3. Draw the electron dot structure for nitrogen trichloride, NCl3.

4. Draw the electron dot configuration for acetylene, C2H2.

5. How many resonance structures can be drawn for CO32�? Show the

electron dot structures for each.

SECTION 8.3 BONDING THEORIES1. Predict the shape and bond angle for the compound carbon

tetrafluoride, CF4.

2. Predict the shape and bond angle for phosphorus trifluoride, PF3.

3. Predict the type of hybridized orbitals involved in the compound borontrichloride, BCl3.

4. What types of hybrid orbitals are involved in the bonding of the siliconatoms in silicon tetrafluoride, SiF4?

5. Predict the shape and bond angle of fluorine monoxide, F2O.

Name ___________________________ Date ___________________ Class __________________

COVALENT BONDING8

© Pearson Education, Inc., publishing as Pearson Prentice Hall. All rights reserved.

05_CTR_ch08 7/12/04 8:12 AM Page 190


6. Predict the shape of the CH2CF2 molecule. What hybridization is involvedin the carbon-carbon bonds?

7. How many sigma and pi bonds are used by each of the carbon atoms inthe following compound?

SECTION 8.4 POLAR BONDS AND MOLECULES1. What type of bond—nonpolar covalent, polar covalent, or ionic—will form

between each pair of atoms?

a. Na and O b. O and O c. P and O

2. Explain why most chemical bonds would be classified as either polarcovalent or ionic.

3. Would you expect carbon monoxide and carbon dioxide to be polar ornonpolar molecules?

4. Draw the structural formulas for each molecule and identify polar covalentbonds by assigning the slightly positive (��) and slightly negative (��)symbols to the appropriate atoms.

a. NH3 b. CF3

5. Which would you expect to have the higher melting point, CaO or CS2?

C1H C2 O HH

H O

Name ___________________________ Date ___________________ Class __________________©

Pears

on Ed

ucati

on, I

nc.,

publi

shing

as Pe

arson

Pren

tice H

all. A

ll righ

ts res

erved

.

05_CTR_ch08 7/12/04 8:12 AM Page 191


Figure 1 Common Molecular Shapes

Use what you have learned in Chapter 8 to complete the table on the following page.

Table 1 Arrangement of electron pairs about an atom

Linear triatomic Trigonal planar Bent triatomic

Trigonal bipyramidalTetrahedralPyramidal

Name ___________________________ Date ___________________ Class __________________©


INTERPRETING GRAPHICSUse with Section 8.3

8

Number of valence electron pairsabout the central atom

Arrangement of valence-electron pairs

2 linear

3 trigonal planar

4 tetrahedral

5 trigonal bipyramidal

05_CTR_ch08 7/12/04 8:12 AM Page 192


Table 2 Molecular Geometries

8. If you have access to a molecular model set, construct three-dimensional modelsof each of the molecules in the table. Compare your models to the shapes shownin Figure 1. With a protractor, measure all the bond angles in your models.Compare these angles to those predicted by VSEPR theory and label each of theillustrations in Figure 1 with the correct bond angles.

Name ___________________________ Date ___________________ Class __________________©

Pears

on Ed

ucati

on, I

nc.,

publi

shing

as Pe

arson

Pren

tice H

all. A

ll righ

ts res

erved

.

Molecule Electron Dot Structure Shape Bond Angle Resonance Structures

1. CO2

2. CH4

3. SO3

4. BeF2

5. PF3

6. PCl5

7. H2O

05_CTR_ch08 7/12/04 8:12 AM Page 193


Name ___________________________ Date ___________________ Class __________________©


COVALENT BONDING8

Vocabulary ReviewSelect the term from the following list that best matches each description.

polyatomic ion VSEPR theory bonding molecular orbitalcoordinate covalent bond sigma bond van der Waals forceshybridization molecule bond dissociation energyhydrogen bond

1. a bond in which one atom contributes both bonding electrons to a covalent bond

2. the total energy required to break the bond between two covalently bonded atoms

3. a molecular orbital whose energy is lower than that of the atomic orbitals fromwhich it is formed

4. molecular orbital that lies along the axis connecting two atomic nuclei

5. states that because electron pairs repel, molecules adjust their shapes so thatvalence-electron pairs are as far apart as possible

6. a process in which several atomic orbitals mix to form the same number ofequivalent hybrid orbitals

7. a tightly bound group of atoms that behaves as a unit and carries a charge

8. a term that collectively refers to dispersion forces and dipole interactions

9. a relatively strong intermolecular attraction in which a hydrogen that iscovalently bonded to a very electronegative atom is also weakly bonded to anunshared pair of electrons of another electronegative atom

10. a tightly connected group of two or more atoms of nonmetallic elements thatbehave as an electrically neutral unit

05_CTR_ch08 7/12/04 8:12 AM Page 194


Chapter QuizChoose the best answer and write its letter on the line.

________ 1. A bond in which each atom contributes two electrons is 8.2a. a double covalent bond. c. a polar covalent bond.b. an ionic bond. d. a coordinate covalent bond.

________ 2. The electron dot structure for hydrogen sulfide, H2S, is 8.2

a. c.

b. d.

________ 3. Which electron dot structure represents a nonpolar molecule? 8.2

a. c.

b. d.

________ 4. Bond dissociation energy 8.2a. is the energy required to break a single bond.b. of a C 2 H bond is high.c. of a C 2 C bond is high.d. all of the above

________ 5. A covalent bond formed between two elements that have an 8.4electronegativity difference of 1.6 would bea. a nonpolar bond. c. a moderately polar bond.b. a very polar bond. d. an ionic bond.

________ 6. You would expect a bond formed between a silicon atom and an 8.4oxygen atom to bea. an ionic bond. c. a polar covalent bond.b. a coordinate covalent bond. d. a nonpolar covalent bond.

Classify each of these statements as always true, AT; sometimes true, ST; or never true, NT.

________ 7. Molecular orbitals involve pi bonding. 8.3

________ 8. An antibonding orbital is a molecular orbital whose energy is lower 8.3than that of the atomic orbitals from which it is formed.

________ 9. A three-atom molecule is bent. 8.3

________ 10. Sigma and pi bonds are found in the same molecule. 8.3

________ 11. A molecule contains two atoms. 8.1

CH FCCl Cl

ClHOH H

SHHSH H

SHH

SHH

Name ___________________________ Date ___________________ Class __________________©

Pears

on Ed

ucati

on, I

nc.,

publi

shing

as Pe

arson

Pren

tice H

all. A

ll righ

ts res

erved

.

COVALENT BONDING8

05_CTR_ch08 7/12/04 8:12 AM Page 195


Chapter Test A

A. MatchingMatch each description in Column B with the correct term in Column A. Write theletter of the correct description on the line.

Column B

a. shows the kinds and numbers present in amolecule of a compound

b. chemical formula that shows the arrangement ofatoms in molecules and polyatomic ions

c. a covalent bond between two atoms of differentelectronegativities in which the bondingelectrons are not shared equally

d. interaction caused by the motion of electrons

e. a covalent bond formed by the equal sharing ofbonding electrons by two atoms

f. a covalent bond involving two pairs of electrons;each atom donates one pair of electrons to thebond

g. a covalent bond in which three pairs of electronsare shared by two bonded atoms

h. substance in which all of the atoms arecovalently bonded to each other

i. a covalent bond between two atoms in which theshared electron pair comes from only one of theatoms

j. force that occurs when a hydrogen atom that iscovalently bonded to a very electronegative atomis also weakly bonded to an unshared pair ofelectrons in the same or a nearby molecule

Column A

coordinate covalent bond

nonpolar covalent bond

hydrogen bond

double covalent bond

dispersion force

molecular formula

structural formula

polar bond

triple covalent bond

network solid

________ 1.

________ 2.

________ 3.

________ 4.

________ 5.

________ 6.

________ 7.

________ 8.

________ 9.

________ 10.

Name ___________________________ Date ___________________ Class __________________©


COVALENT BONDING8

05_CTR_ch08 7/12/04 8:12 AM Page 196


B. Multiple ChoiceChoose the best answer and write its letter on the line.

________ 11. Which of these elements does not exist as a diatomic molecule?a. I c. Hb. F d. He

________ 12. Which one of the following compounds is not covalent?a. SCl2 c. HClb. KCl d. S2Cl2

________ 13. How many valence electrons does an atom of any halogen have?a. 1 c. 4b. 2 d. 7

________ 14. A diatomic molecule with a triple covalent bond isa. N2. c. H2.b. Br2. d. O2.

________ 15. A molecule of nitrous oxide, N2O, contains all of the following excepta. a coordinate covalent bond. c. a double bond.b. a triple bond. d. nonbonding pairs of electrons.

________ 16. If a bonding pair of electrons is unequally shared between two atoms,the bond isa. ionic. c. coordinate covalent.b. nonpolar covalent. d. polar covalent.

________ 17. What is the electron dot structure for water?a. H 6 6 O 6 6 H c.

b. d.

________ 18. Which of the following compounds is not ionic?a. NaI c. CO2

b. CaCl2 d. Na2O

________ 19. A covalent bond formsa. when an element becomes a noble gas.b. when atoms share electrons.c. between metals and nonmetals.d. when electrons are transferred from one atom to another.

________ 20. What is the electron dot structure for the polyatomic ion OH�?a. c.

b. d.

________ 21. Which of these compounds would not have covalent bonds?a. NO2 c. N2O4

b. K2O d. H2O2

[ O H]�[H O ]�

[H O]�[ O H]�

H

OHOHH

HOH

N 4 N y O

Name ___________________________ Date ___________________ Class __________________©

Pears

on Ed

ucati

on, I

nc.,

publi

shing

as Pe

arson

Pren

tice H

all. A

ll righ

ts res

erved

.

05_CTR_ch08 7/12/04 8:12 AM Page 197


________ 22. A molecule with a single covalent bond isa. CO2. c. NO.b. F2. d. N2.

________ 23. Chlorine is a gas, bromine is a liquid, and iodine is a solid because ofdifferences in the strength of theira. hydrogen bonds. c. dipole interactions.b. dispersion forces. d. polar bonds.

________ 24. When H� forms a bond with H2O to form hydronium ion, H3O�, thisbond is called a coordinate covalent bond becausea. both bonding electrons come from the oxygen atom.b. it is an especially strong bond.c. the electrons are equally shared.d. the oxygen no longer has eight electrons surrounding it.

________ 25. Which of the following molecules has one lone pair of electrons?a. CH4 c. H2Ob. HCl d. NH3

________ 26. Which of the following is the weakest?a. hydrogen bond c. dipole interactionb. polar covalent bond d. ionic bond

________ 27. The carbon tetrachloride molecule isa. four-cornered. c. tetrahedral.b. square. d. pyramidal.

C. QuestionsAnswer the following questions in the space provided.

28. Draw structural formulas for the following substances.

a. Br2

b. N2

c. CO

29. State whether the following compounds contain polar covalent bonds, nonpolarcovalent bonds, or ionic bonds. (You may refer to the table of electronegativitieson the top of the next page.)

a. KF

b. SO2

c. NO2

d. HBr

Name ___________________________ Date ___________________ Class __________________©


05_CTR_ch08 7/12/04 8:12 AM Page 198


Reference Section

30. The following covalent molecules have only single covalent bonds. Draw anelectron dot structure for each one.

a. HBr c. PCl3

b. H2O2

D. Essay31. Describe a network solid and give two examples.

E. Additional Questions and ProblemsAnswer the following in the space provided. Show your work.

32. Calculate the total energy needed to dissociate all the bonds in one mole ofethyl alcohol, C2H5OH. (Assume that the total energy is the sum of theindividual bond dissociation energies.) The structural formula of ethyl alcohol is

Bond Energy (kJ/mol)H 2 H 435C 2 H 393C 2 O 356O 2 H 464C 2 C 347

H

O 2

C 2 H

H

H 2 C 2

H

H

@

@

@

@

Name ___________________________ Date ___________________ Class __________________©

Pears

on Ed

ucati

on, I

nc.,

publi

shing

as Pe

arson

Pren

tice H

all. A

ll righ

ts res

erved

.

Electronegativities

1A 0

H2.1 2A 3A 4A 5A 6A 7A

He—

Li1.0

Be1.5

B2.0

C2.5

N3.0

O3.5

F4.0

Ne—

Na0.9

Mg1.2

Al 1.5

Si1.8

P 2.1

S 2.5

Cl 3.0

Ar—

K0.8

Ca 1.0

Ga 1.6

Ge 1.8

As 2.0

Se 2.4

Br 2.8

Kr—

05_CTR_ch08 7/12/04 8:12 AM 9


33. With the aid of a diagram, describe how the overlap of one 2p orbital from eachof two atoms forms a sigma bond, but the overlap of the remaining two 2porbitals from each atom forms pi bonds.

34. Indicate the hybrid orbitals used by each carbon atom in the followingcompound. The carbons are numbered for easy reference.

35. Draw electron dot structures for PCl5 and SF6. (Hint: These compounds areexceptions to the octet rule.)

H C C C

H

H

C

O

C

H

H

H1 2 3 4 5

Name ___________________________ Date ___________________ Class __________________©


05_CTR_ch08 7/12/04 8:12 AM 0


Chapter Test B

A. MatchingMatch each term in Column B with the correct description in Column A. Write theletter of the correct term on the line.

Column B

a. molecular compound

b. VSEPR theory

c. van der Waals forces

d. single covalent bond

e. resonance structures

f. polar molecule

g. hybridization

h. structural formula

i. polar covalent bond

j. coordinate covalent bond

Column A

the mixing of several atomic orbitals to form the samenumber of equivalent hybrid orbitals

two or more valid electron dot formulas that can bewritten for the same molecule

a chemical formula that shows the arrangement ofatoms in molecules and polyatomic ions

the weakest attractions that exist between molecules

Because electron pairs repel, molecules adjust theirshapes so that the valence-electron pairs are as farapart as possible.

a covalent bond in which one pair of electrons isshared between two atoms

a molecule in which one end is slightly negative andthe other end is slightly positive

a covalent bond formed between two different atomsin which the bonding electrons are shared unequally

an electrically neutral group of atoms joined togetherby covalent bonds

a covalent bond in which one atom contributes bothbonding electrons

________ 1.

________ 2.

________ 3.

________ 4.

________ 5.

________ 6.

________ 7.

________ 8.

________ 9.

________ 10.

Name ___________________________ Date ___________________ Class __________________©

Pears

on Ed

ucati

on, I

nc.,

publi

shing

as Pe

arson

Pren

tice H

all. A

ll righ

ts res

erved

.

COVALENT BONDING8

05_CTR_ch08 7/12/04 8:12 AM Page 201


B. Multiple ChoiceChoose the best answer and write its letter on the line.

________ 11. Which of the following exists as a diatomic molecule?a. He c. Clb. Ar d. Na

________ 12. The diatomic molecule among the following that contains a singlecovalent bond isa. F2. c. N2.b. O2. d. O2�.

________ 13. Atoms share electrons in order to acquire the electron configurations ofa. alkali metals. c. halogens.b. alkaline earth metals. d. noble gases.

________ 14. In Cl2, what is the total number of unshared pairs of electrons?a. 1 c. 4b. 2 d. 6

________ 15. The diatomic molecule among the following that contains a triplecovalent bond isa. O2. c. H2.b. Cl2. d. N2.

________ 16. In the N2 molecule, what is the number of unshared pairs of electronsin each nitrogen atom?a. 1 c. 3b. 2 d. 4

________ 17. The covalent molecule among the following isa. NaCl. c. CaO.b. NH3. d. KF.

________ 18. How many single covalent bonds are there in a molecule of CH4?a. 1 c. 3b. 2 d. 4

________ 19. How many double covalent bonds are there in a molecule of CO2?a. 1 c. 3b. 2 d. 4

________ 20. The molecule among the following that contains only one singlecovalent bond isa. NH3. c. HI.b. N2. d. H2O.

________ 21. In forming the molecule HF, the F atom attains the electronconfiguration ofa. He. c. Ar.b. Ne. d.. Cl.

Name ___________________________ Date ___________________ Class __________________©


05_CTR_ch08 7/12/04 8:12 AM Page 202


________ 22. Which molecule among the following contains a coordinate covalentbond?a. CO c. H2Ob. NH3 d. CCl4

________ 23. The molecule among the following that exhibits resonance structures isa. CO2. c. O3 (ozone).b. CH4. d. NH3.

________ 24. Resonance structures can be considereda. polar molecules. c. coordinate covalent molecules.b. hybrids. d. none of the above

________ 25. Substances that show relatively strong attractions to an externalmagnetic field are said to bea. diamagnetic. c. nonmagnetic.b. paramagnetic. d. none of the above

________ 26. Oxygen is an example of a substance that isa. diamagnetic. c. nonmagnetic.b. paramagnetic. d. none of the above

________ 27. When two atomic orbitals combine to form a molecular orbital that issymmetrical along the axis connecting the two atomic nuclei, thebond that is produced is referred to as a(n)a. ionic bond. c. sigma bond.b. pi bond. d. none of the above

________ 28. The shape of a molecule of NH3 is said to bea. tetrahedral. c. bent.b. pyramidal. d. linear.

________ 29. In a methane (CH4) molecule, the mixing of one 2s orbital with three2p orbitals formsa. one sp4 hybrid orbital. c. one sp3 hybrid orbital.b. four sp hybrid orbitals. d. four sp3 hybrid orbitals.

________ 30. The overlap of atomic s orbitals produces a(n)a. ionic bond. c. sigma bond.b. pi bond. d. none of the above

________ 31. Which of the following contains a polar covalent bond?a. O2 c. CaOb. MgCl2 d. HF

________ 32. What type of bond would be expected in a molecule of LiF?a. ionic bond c. nonpolar covalent bondb. polar covalent bond d. none of the above

Name ___________________________ Date ___________________ Class __________________©

Pears

on Ed

ucati

on, I

nc.,

publi

shing

as Pe

arson

Pren

tice H

all. A

ll righ

ts res

erved

.

05_CTR_ch08 7/12/04 8:12 AM Page 203

________ 33. Among the following molecules, the one containing the most polarbond isa. HF. c. HBr.b. HCl. d. H2O.

________ 34. The polar molecule among the following isa. CCl4. c. H2O.b. CO2. d. N2.

________ 35. The strongest intermolecular attractive forces from among those listed area. dispersion forces. c. hydrogen bonds.b. dipole interactions. d. cannot be determined

________ 36. The melting and boiling points of most molecular compounds area. lower than those of most ionic compounds.b. about the same as those of most ionic compounds.c. higher than those of most ionic compounds.d. sometimes higher and sometimes lower than those of most ionic

compounds.

________ 37. Network solidsa. have low melting points. c. are extremely hard.b. have low boiling points. d. are generally ductile.

C. QuestionsAnswer the following in the space provided.

38. Write both the electron dot structure and the structural formula for each of thefollowing covalent molecules:

Name ___________________________ Date ___________________ Class __________________©


Electron Dot Structure Structural Formula

a. H2

b. N2

c. H2O

d. NH3

e. CO


05_CTR_ch08 7/12/04 8:12 AM Page 204


39. Write the electron dot formula for each of the following polyatomic ions.

a. NH4�

b. PO43�

D. Essay40. Distinguish between ionic and covalent bonds in terms of how each is formed and how to predict

which will be formed when various elements combine.

Name ___________________________ Date ___________________ Class __________________©

Pears

on Ed

ucati

on, I

nc.,

publi

shing

as Pe

arson

Pren

tice H

all. A

ll righ

ts res

erved

.

05_CTR_ch08 7/12/04 8:12 AM Page 205


E. Additional Questions and ProblemsAnswer the following in the space provided. Show your work.

41. Use the electronegativity table below to determine the type of bond (polarcovalent, nonpolar covalent, or ionic) that would be formed between each ofthe following elements. Give the electronegativity difference in each case.

Reference Section

42. Given the following bond dissociation energy values, calculate the total energy thatwould be required to break all of the covalent bonds in 0.25 mol of ethane (C2H6).C�C = 347 kJ/mol and C�H = 393 kJ/mol

Name ___________________________ Date ___________________ Class __________________©


Electronegativities

1A 0

H2.1 2A 3A 4A 5A 6A 7A

He—

Li1.0

Be1.5

B2.0

C2.5

N3.0

O3.5

F4.0

Ne—

Na0.9

Mg1.2

Al 1.5

Si1.8

P 2.1

S 2.5

Cl 3.0

Ar—

K0.8

Ca 1.0

Ga 1.6

Ge 1.8

As 2.0

Se 2.4

Br 2.8

Kr—

Bond Type Electronegativity Difference

a. H, Cl

b. H, S

c. S, Cl

d. Na, F

e. Cl, Br

f. Al, Br

05_CTR_ch08 7/12/04 8:12 AM Page 206

05 CTR ch08 7/12/04 8:12 AM Page 181 MOLECULAR...

Documents

Transcript of 05 CTR ch08 7/12/04 8:12 AM Page 181 MOLECULAR...