Chemistry The Science in Context

Thomas R. Gilbert

Chapter 8

Chemical Bonds: What Makes a Gas a Greenhouse Gas? - all with Video Answers

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Chapter Questions

Problem 1

Which group highlighted in Figure P8.1 contains atoms that have the following? (a) 1 valence electron; (b) 4 valence electrons; (c) 6 valence electrons

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Problem 2

Which of the groups highlighted in Figure P8.2 contains atoms with the following? (a) 2 valence electrons; (b) 3 valence electrons; (c) 5 valence electrons

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Problem 3

Which of the Lewis symbols in Figure P8.3 correctly portrays the most stable ion of magnesium?

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Problem 4

What changes must be made to the Lewis symbols in Figure P8.4 to make them correct?

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Problem 5

Which of the highlighted elements in Figure P8.5 has the greatest bonding capacity?

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Problem 6

Which of the highlighted elements in Figure P8.6 has the greatest electronegativity?

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Problem 7

Which two of the highlighted elements in Figure P8.6 form the bonding pair with the most ionic character? Note: The color scale used in Problems $8.8,8.9,8.12,$ and 8.13 is the same as in Figure $8.5,$ where violet is a charge of $1+,$ red is a charge of
$1-,$ and green is $0 .$ The larger the size, the greater the electron density.

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Problem 8

Which of the drawings in Figure P8.8 is the best description of the distribution of electrical charge in ClBr?

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Problem 9

Which of the drawings in Figure P8.9 best describes the distribution of electrical charge in LiF?

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Problem 10

Are the three structures in Figure $\mathrm{P} 8.10$ resonance forms of the thiocyanate ion $\left(\mathrm{SCN}^{-}\right) ?$ Explain why or why not.

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Problem 11

Why are the structures in Figure $\mathrm{P} 8.11$ not all resonance forms of the molecule $\mathrm{S}_{2} \mathrm{O} ?$

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Problem 12

Which of the drawings in Figure P8.12 most accurately describes the distribution of electrical charge in ozone? Explain your answer.

David Collins

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Problem 13

Which of the drawings in Figure P8.13 most accurately describes the distribution of electrical charge in $\mathrm{SO}_{2} ?$ Explain your answer.

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Problem 14

How many electron pairs are shared in each of the molecules and ions in Figure $\mathrm{P} 8.14 ?$

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Problem 15

Krypton and xenon form compounds with only the most reactive of other elements. Which of the highlighted elements in Figure $\mathrm{P} 8.15$ is one of these highly reactive elements?

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Problem 16

What changes must be made to the Lewis structures in Figure $\mathrm{P} 8.16$ to make them correct? Assume the skeletal structures shown are correct.

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Problem 17

In each pair of resonance structures in Figure P8.17, which one contributes more to the bonding in the molecule or molecular ion?

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Problem 18

Use representations $[\mathrm{A}]$ through $[\mathrm{I}]$ in Figure P8.18 to answer questions a-f.
a. Which hydrocarbon has the strongest carbon-carbon bond?
b. Which hydrocarbon has the weakest carbon-carbon bond?
c. Could [B] and/or [G] absorb an infrared photon through an asymmetric stretch and contribute to the greenhouse effect?
d. Label the most polar bond in $[\mathrm{C}]$ and in $[\mathrm{D}],$ using both the arrow $(\leftrightarrow)$ and $\delta+$ and $\delta-$ notations.
e. Which process is exothermic?
F. Which representation demonstrates a key limitation of Lewis structures?

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Problem 19

Does the number of valence electrons in a neutral atom ever equal the atomic number?

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Problem 20

Does the number of valence electrons in a neutral atom ever equal the group number?

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Problem 21

Do all the elements in a group in the periodic table hav the same number of valence electrons?

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Problem 22

Distinguish between an atom's valence electrons and its total electron count.

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Problem 23

Some of his critics described G. N. Lewis's approach to explaining covalent bonding as an exercise in double counting and therefore invalid. Explain the basis for this criticism.

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Problem 24

Does the octet rule mean that a diatomic molecule must have 16 valence electrons?

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Problem 25

Why would you not expect to find hydrogen atoms in the bonding arrangement $\mathrm{X}-\mathrm{H}-\mathrm{X} ?$

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Problem 26

Does each atom in a pair that is covalently bonded always contribute the same number of valence electrons to form the bonds between them?

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Problem 27

Draw Lewis symbols of atoms of lithium, magnesium, and aluminum.

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Problem 28

Draw Lewis symbols of atoms of nitrogen, oxygen, fluorine, and chlorine.

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Problem 29

Find the error in each of the Lewis symbols in Figure P8.29.

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Problem 30

Find the error in each of the Lewis symbols in Figure P8.30.

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Problem 31

Draw Lewis symbols for $\operatorname{In}^{+}, \mathrm{I}^{-}, \mathrm{Ca}^{2+},$ and $\mathrm{Sn}^{2+} .$ Which ions have a complete valence-shell octet?

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Problem 32

Draw Lewis symbols of $\mathrm{Xe}, \mathrm{Sr}^{2+}, \mathrm{Cl},$ and $\mathrm{Cl}^{-} .$ How many valence electrons are in each atom or ion?

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Problem 33

Draw the Lewis symbol of an ion that has the following:
a. $1+$ charge and 1 valence electron
b. $3+$ charge and 0 valence electrons

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Problem 34

Draw the Lewis symbol of an ion that has the following:
a. $1-$ charge and 8 valence electrons
b. $1+$ charge and 5 valence electrons

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Problem 35

How many valence electrons does each of the following species contain? (a) $\mathrm{BN} ;$ (b) $\mathrm{HF} ;$ (c) $\mathrm{OH}^{-} ;$ (d) $\mathrm{CN}^{-}$.

Allison Krajewski

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Problem 36

How many valence electrons does each of the following species contain? (a) $\mathrm{N}_{2}^{+} ;$ (b) $\mathrm{CS}^{+} ;$ (c) $\mathrm{CN} ;$ (d) CO.

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Problem 37

Draw Lewis structures for the following diatomic molecules and ions: (a) $\mathrm{CO}_{i}$ (b) $\mathrm{O}_{2}$; (c) $\mathrm{ClO}^{-}$; (d) $\mathrm{CN}^{-}$.

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Problem 38

Draw Lewis structures for the following diatomic molecules and ions: (a) $\mathrm{F}_{2} ;$ (b) $\mathrm{NO}^{+} ;$ (c) $\mathrm{SO} ;$ (d) HI.

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Problem 39

Which groups among main group elements have an odd number of valence electrons?

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Problem 40

Which of the groups in the periodic table will carry negative partial charges in diatomic compounds with hydrogen, HX and $\mathrm{H}_{2} \mathrm{X} ?$

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Problem 41

Greenhouse Gases Chlorofluorocarbons (CFCs) are linked to the depletion of stratospheric ozone. They are also greenhouse gases. Draw Lewis structures for the following CFCs:
a. $\left.\mathrm{CF}_{2} \mathrm{Cl}_{2} \text { (Freon } 12\right)$
b. $\left.\mathrm{Cl}_{2} \mathrm{FCCF}_{2} \mathrm{Cl} \text { (Freon } 113, \text { containing a } \mathrm{C}-\mathrm{C} \text { bond }\right)$
c. $\mathrm{C}_{2} \mathrm{ClF}_{3}$ (Freon 1113 , containing a $\mathrm{C}=\mathrm{C}$ bond).

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Problem 42

Draw Lewis structures for the organic compounds shown and answer the following questions. Assume the skeletal structures in Figure P8.42 are correct.
a. Which of these molecules is an alkyne?
b. Which molecule has the shortest carbon-carbon bond(s)?
c. Which of these molecules contains an aldehyde functional group?

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Problem 43

Skunks and Rotten Eggs Many sulfur-containing organic compounds have characteristically foul odors: butanethiol $\left(\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{SH}\right)$ is responsible for the odor of
skunks, and rotten eggs smell the way they do because they produce tiny amounts of pungent hydrogen sulfide, $\mathrm{H}_{2} \mathrm{S} .$ Draw the Lewis structures for $\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{SH}$
and $\mathrm{H}_{2} \mathrm{S}$.

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Problem 44

Acid in Ants Formic acid, HCOOH, is the smallest organic acid and was originally isolated by distilling red ants. Draw its Lewis structure given the connectivity of the atoms as shown in Figure P8.44.

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Problem 45

Chlorine Bleach Chlorine combines with oxygen in several proportions. Dichlorine monoxide (Cl $_{2} \mathrm{O}$ ) is used in the manufacture of bleaching agents. Potassium chlorate $\left(\mathrm{KClO}_{3}\right)$ is used in oxygen generators aboard aircraft. Draw the Lewis structures for $\mathrm{Cl}_{2} \mathrm{O}$ and $\mathrm{ClO}_{3}^{-}$.

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Problem 46

Dangers of Mixing Cleansers Labels on household cleansers caution against mixing bleach with ammonia (Figure $\mathrm{P} 8.46)$ because the reaction produces monochloramine (NH_CCl) and hydrazine (N $_{2} \mathrm{H}_{4}$ ), both of which are toxic:
$$
\begin{aligned}
\mathrm{NH}_{3}(a q)+\mathrm{OCl}^{-}(a q) \rightarrow \mathrm{NH}_{2} \mathrm{Cl}(a q)+\mathrm{OH}^{-}(a q) \\
\mathrm{NH}_{2} \mathrm{Cl}(a q)+\mathrm{NH}_{3}(a q)+\mathrm{OH}^{-}(a q) \rightarrow \\
\mathrm{N}_{2} \mathrm{H}_{4}(a q)+\mathrm{Cl}^{-}(a q)+\mathrm{H}_{2} \mathrm{O}(\ell)
\end{aligned}
$$
Draw the Lewis structures for monochloramine and hydrazine.

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Problem 47

How can we use electronegativity to predict whether a bond between two atoms is likely to be covalent or ionic?

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Problem 48

How do the electronegativities of the elements change across a period and down a group?

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Problem 49

Explain on the basis of atomic structure why trends in electronegativity are related to trends in atomic size.

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Problem 50

Is the element with the most valence electrons in a period also the most electronegative? Explain.

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Problem 51

What is meant by the term polar covalent bond?

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Problem 52

What factor is responsible for the existence of polar covalent bonds?

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Problem 53

Describe how atmospheric greenhouse gases act like the panes of glass in a greenhouse.

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Problem 54

Understanding the Greenhouse Effect Water vapor in the atmosphere contributes more to the greenhouse effect than carbon dioxide, yet water vapor is not considered an important factor in global warming. Propose a reason why.

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Problem 55

Increasing concentrations of nitrous oxide in the atmosphere may be contributing to climate change. Is the ability of $\mathrm{N}_{2} \mathrm{O}$ to absorb infrared radiation due to nitrogen-nitrogen bond stretching, nitrogen-oxygen bond stretching, or both? Explain your answer.

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Problem 56

Is the ability of $\mathrm{H}_{2} \mathrm{O}$ molecules to absorb photons of infrared radiation due to symmetrical stretching or asymmetrical stretching of its $\mathrm{O}-\mathrm{H}$ bonds, or both? Explain your answer. (Hint: The angle between the two $\mathrm{O}-\mathrm{H}$ bonds in $\mathrm{H}_{2} \mathrm{O}$ is $104.5^{\circ} .$

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Problem 57

Which of the following bonds are polar: $\mathrm{C}-\mathrm{Se}, \mathrm{C}-\mathrm{O}$ $\mathrm{Cl}-\mathrm{Cl}, \mathrm{O}=\mathrm{O}, \mathrm{N}-\mathrm{H}, \mathrm{C}-\mathrm{H} ?$ In the bond or bonds that
you selected, which atom has the greater electronegativity?

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Problem 58

Which is the least polar bond: $C-S e, C=O, C 1-B r$ $\mathrm{O}=\mathrm{O}, \mathrm{N}-\mathrm{H}, \mathrm{C}-\mathrm{H} ?$

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Problem 59

In which of the following binary compounds is the bond expected to have the least ionic character? LiCl; Cs I; $\mathrm{KBr} ; \mathrm{NaF}$.

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Problem 60

In which of the following compounds is the bond between the atoms expected to have the most covalent character? $\mathrm{AlCl}_{3} ; \mathrm{AlBr}_{3} ; \mathrm{AlI}_{3} ; \mathrm{GaF}_{3}$.

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Problem 61

Which polar bond in Figure $\mathrm{P} 8.61$ is correctly labeled?

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Problem 62

Which polar bond in Figure $\mathrm{P} 8.62$ is correctly labeled?

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Problem 63

Which bond in the following is correctly labeled?
$$\begin{array}{lll}
\delta-\delta+ & \delta-\delta+ & \delta-\delta+ \\
O-H & C-C l & B r-B r
\end{array}$$

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Problem 64

Which bond in the following is correctly labeled?
$$
\begin{array}{lll}
\delta+\delta- & \delta+\delta- & \delta+\delta- \\
\mathrm{Na}-\mathrm{Cl} & \mathrm{Li}-\mathrm{F} & \mathrm{Si}-\mathrm{F}
\end{array}
$$

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Problem 65

Which substance has the most polar covalent bonds: $\mathrm{PF}_{3}$
$\mathrm{S}_{8}, \mathrm{RbCl},$ or $\mathrm{SF}_{2} ?$

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Problem 66

Atoms of which element are held together by nonpolar covalent bonds: lithium, phosphorus, or xenon?

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Problem 67

Explain the concept of resonance.

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Problem 68

How does resonance influence the stability of a molecule or an ion?

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Problem 69

What factors determine whether a molecule or ion exhibits resonance?

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Problem 70

What structural features do all the resonance forms of a molecule or ion have in common?

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Problem 71

Explain why $\mathrm{NO}_{2}$ is more likely to exhibit resonance than $\mathrm{CO}_{2}$.

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Problem 72

Are these two skeletal structures resonance forms:
$\mathrm{X}-\mathrm{X}-\mathrm{O}$ and $\mathrm{X}-\mathrm{O}-\mathrm{X} ?$ Explain.

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Problem 73

Draw Lewis structures for fulminic acid (HCNO), showing all resonance forms.

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Problem 74

Draw Lewis structures for hydrazoic acid (HN $_{3}$ ), showing all resonance forms.

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Problem 75

Oxygen and nitrogen combine to form a variety of nitrogen oxides, including the following two unstable compounds, each with two nitrogen atoms per molecule: $\mathrm{N}_{2} \mathrm{O}_{2}$ and $\mathrm{N}_{2} \mathrm{O}_{3} .$ Draw Lewis structures for these molecules, showing all resonance forms.

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Problem 76

Oxygen and sulfur combine to form a variety of sulfur oxides. Some are stable molecules and some, including $\mathrm{S}_{2} \mathrm{O}_{2}$ and $\mathrm{S}_{2} \mathrm{O}_{3},$ decompose when they are heated. Draw Lewis structures for these two compounds, showing all resonance forms.

Aadit Sharma

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Problem 77

The oxygen-oxygen distance in $\mathrm{F}_{2} \mathrm{O}_{2}$ is about $20 \%$ shorter than in hydrogen peroxide.
a. Draw Lewis structures for both $\mathrm{F}_{2} \mathrm{O}_{2}$ and $\mathrm{H}_{2} \mathrm{O}_{2}$
b. It was proposed that $\mathrm{F}_{2} \mathrm{O}_{2}$ has a resonance form of $\left[\mathrm{FO}_{2}\right]^{+} \mathrm{F}^{-} .$ Draw a Lewis structure for this "ionic" form of $\mathrm{F}_{2} \mathrm{O}_{2}$ and explain how the structure is consistent with the observed O-O distance.

Aadit Sharma

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Problem 78

The nitrogen-oxygen bond distance in $\mathrm{NOF}_{3}$ is shorter than in $\mathrm{NO}\left(\mathrm{CH}_{3}\right)_{3}$
a. Draw Lewis structures for $\mathrm{NOF}_{3}$ and $\mathrm{NO}\left(\mathrm{CH}_{3}\right)_{3}$
b. It was proposed that $\mathrm{NOF}_{3}$ has a resonance form of $\left[\mathrm{NOF}_{2}\right]^{+} \mathrm{F}^{-} .$ Draw a Lewis structure for this "ionic" form of $\mathrm{NOF}_{3}$ and explain how the structure is consistent with the observed $\mathrm{N}$ - $\mathrm{O}$ distance.

Aadit Sharma

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Problem 79

Chemists can use the octet rule to predict the structures of new compounds to synthesize. Draw Lewis structures showing all resonance forms for the hypothetical compound ClSeNSO, where the atoms are connected in the order they are written.

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Problem 80

Aromatic rings can connect to make larger molecules. The skeletal structures of two such molecules are shown in Figure P8.80. Draw Lewis structures for both molecules, showing all resonance forms.

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Problem 81

Describe how formal charges are used to choose between possible molecular structures.

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Problem 82

How do the electronegativities of elements influence the selection of which Lewis structure is favored?

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Problem 83

In a molecule containing $\mathrm{S}$ and $\mathrm{O}$ atoms, is a structure with a negative formal charge on sulfur more likely to contribute to bonding than an alternative structure with a negative formal charge on oxygen? Explain.

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Problem 84

In a cation containing $\mathrm{N}$ and $\mathrm{O},$ why do Lewis structures with a positive formal charge on nitrogen contribute more to the actual bonding in the molecule than do those structures with a positive formal charge on oxygen?

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Problem 85

Hydrogen isocyanide (HNC) has the same elemental composition as hydrogen cyanide (HCN), but the H atom in HNC is bonded to the nitrogen atom. Draw a Lewis structure for HNC and assign formal charges to each atom. How do the formal charges on the atoms differ in the Lewis structures for HCN and HNC?

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Problem 86

Molecules in Interstellar Space Hydrogen cyanide (HCN) and cyanoacetylene (HC $_{3}$ N) have been detected in the interstellar regions of space and in comets close to Earth (Figure $\mathrm{P} 8.86$ ). Draw Lewis structures for these molecules, and assign formal charges to each atom. The hydrogen atom is bonded to the carbon atom in both cases.

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Problem 87

Origins of Life The discovery of polyatomic organic molecules such as cyanamide (H $_{2} \mathrm{NCN}$ ) in interstellar space has led some scientists to believe that the molecules from which life began on Earth may have come from space. Draw Lewis structures for cyanamide, and select the preferred structure on the basis of formal charges.

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Problem 88

Nitromethane $\left(\mathrm{CH}_{3} \mathrm{NO}_{2}\right)$ reacts with hydrogen cyanide to produce CNNO $_{2}$ and $\mathrm{CH}_{4}$ :
$\mathrm{HCN}(g)+\mathrm{CH}_{3} \mathrm{NO}_{2}(g) \rightarrow \mathrm{CNNO}_{2}(g)+\mathrm{CH}_{4}(g)$
a. Draw Lewis structures for $\mathrm{CH}_{3} \mathrm{NO}_{2}$, showing all resonance forms.
b. Draw Lewis structures for CNNO $_{2}$, showing all resonance forms, based on the two possible skeletal structures for it shown in Figure P8.88. Assign formal charges, and predict which structure is more likely to exist.
c. Are the two structures of CNNO $_{2}$ resonance forms of each other?

Madi Sousa

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Problem 89

The formaldehyde molecule contains one carbon atom, one oxygen atom, and two hydrogen atoms. Lewis structures can be drawn that have either carbon or oxygen as the central atom.
a. Draw these structures and use formal charges to predict the more likely structure for formaldehyde.
b. Are the two structures you drew resonance forms of each other?

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Problem 90

Draw all resonance forms of the sulfur-nitrogen anion, $\mathrm{S}_{4} \mathrm{N}^{-},$ and assign formal charges. The atoms are arranged as SSNSS.

Ronald Prasad

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Problem 91

Nitrogen is the central atom in molecules of nitrous oxide $\left(\mathrm{N}_{2} \mathrm{O}\right) .$ Draw Lewis structures for another possible arrangement: $\mathrm{N}-\mathrm{O}-\mathrm{N} .$ Assign formal charges and suggest a reason why this structure is not likely to be stable.

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Problem 92

Use formal charges to determine which resonance form of each of the following ions is preferred: CNO"; NCO"; $\mathrm{CON}^{-}$.

Ronald Prasad

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Problem 93

Are all odd-electron molecules exceptions to the octet rule?

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Problem 94

Describe the factors that contribute to the stability of structures in which the central atoms have more than eight valence electrons.

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Problem 95

Why do $\mathrm{C}, \mathrm{N}, \mathrm{O},$ and $\mathrm{F}$ atoms in covalently bonded molecules and ions have no more than eight valence electrons?

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Problem 96

Do atoms with $Z>12$ always expand their valence shell? Explain your answer.

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Problem 97

In which of the following molecules does the sulfur atom have an expanded valence shell? (a) $\mathrm{SF}_{6} ;$ (b) $\mathrm{SF}_{5} ;$ (c) $\mathrm{SF}_{4}$ (d) $\mathrm{SF}_{2}$.

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Problem 98

In which of the following molecules does the phosphorus atom have an expanded valence shell? (a) $\mathrm{POCl}_{3} ;$ (b) $\mathrm{PF}_{5}$
(c) $\left.\mathrm{PF}_{3} ; \text { (d) } \mathrm{P}_{2} \mathrm{F}_{4} \text { (which has a } \mathrm{P}-\mathrm{P} \text { bond }\right)$.

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Problem 99

How many electrons are there in the covalent bonds surrounding the central atom in the following species?
(a) $\left(\mathrm{CH}_{3}\right)_{3} \mathrm{Al} ;$ (b) $\mathrm{B}_{2} \mathrm{Cl}_{4} ;$ (c) $\mathrm{SO}_{3} ;$ (d) $\mathrm{SF}_{5}^{-}$.

Sam Limsuwannarot

Sam Limsuwannarot

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Problem 100

How many electrons are there in the covalent bonds surrounding the central atom in the following species?
(a) $\mathrm{POCl}_{3} ;(\mathrm{b}) \mathrm{InCl}_{5}^{2-} ;(\mathrm{c}) \mathrm{FBO} ;(\mathrm{d}) \mathrm{PF}_{4}^{-}$.

Sam Limsuwannarot

Sam Limsuwannarot

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Problem 101

Draw Lewis structures for $\mathrm{NOF}_{3}$ and $\mathrm{POF}_{3}$ in which the group 15 element is the central atom and the other atoms are bonded to it. What differences are there in the types of bonding in these molecules?

Sam Limsuwannarot

Sam Limsuwannarot

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Problem 102

The phosphate anion is common in minerals. The corresponding nitrogen-containing anion, $\mathrm{NO}_{4}^{3-},$ is unstable but can be prepared by reacting sodium nitrate with sodium oxide at $300^{\circ} \mathrm{C}$. Draw Lewis structures for each anion. What are the differences in bonding between these ions?

Madi Sousa

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Problem 103

Dissolving NaF in selenium tetrafluoride (SeF $_{4}$ ) produces NaSeF $_{5 .}$ Draw Lewis structures for $\operatorname{SeF}_{4}$ and $\operatorname{SeF}_{5}$. In which structure does Se have more than eight valence electrons?

Sam Limsuwannarot

Sam Limsuwannarot

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Problem 104

Reaction between $\mathrm{NF}_{3}, \mathrm{F}_{2},$ and $\mathrm{SbF}_{3}$ at $200^{\circ} \mathrm{C}$ and 100 atm pressure gives the ionic compound $\mathrm{NF}_{4} \mathrm{SbF}_{6}$
$$
\mathrm{NF}_{3}(g)+2 \mathrm{F}_{2}(g)+\mathrm{SbF}_{3}(g) \rightarrow \mathrm{NF}_{4} \mathrm{SbF}_{6}(s)
$$
Draw Lewis structures for the ions in this product.

Nicole Basile

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Problem 105

Ozone Depletion The compound $\mathrm{Cl}_{2} \mathrm{O}_{2}$ may play a role in ozone depletion in the stratosphere. In the laboratory, reaction of $\mathrm{FClO}_{2}$ with aluminum chloride produces $\mathrm{Cl}_{2} \mathrm{O}_{2}$ and AIFCl_:
$$
\mathrm{FClO}_{2}(g)+\mathrm{AlCl}_{3}(s) \rightarrow \mathrm{Cl}_{2} \mathrm{O}_{2}(g)+\mathrm{AlFCl}_{2}(s)
$$
Draw a Lewis structure for $\mathrm{Cl}_{2} \mathrm{O}_{2}$ based on the arrangement of atoms in Figure $\mathrm{P} 8.105 .$ Does either of the chlorine atoms in the structure have an expanded valence shell?

Sam Limsuwannarot

Sam Limsuwannarot

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Problem 106

Trimethylaluminum reacts with dimethylamine, $\left(\mathrm{CH}_{3}\right)_{2} \mathrm{NH},$ forming methane and $\mathrm{Al}_{2}\left(\mathrm{CH}_{3}\right)_{4}\left[\mathrm{N}\left(\mathrm{CH}_{3}\right)_{2}\right]_{2}$
by the balanced chemical equation:
$2\left(\mathrm{CH}_{3}\right)_{3} \mathrm{Al}+2 \mathrm{HN}\left(\mathrm{CH}_{3}\right)_{2} \rightarrow$
$$
2 \mathrm{CH}_{4}+\mathrm{Al}_{2}\left(\mathrm{CH}_{3}\right)_{4}\left[\mathrm{N}\left(\mathrm{CH}_{3}\right)_{2}\right]_{2}
$$
Draw the Lewis structures for the reactants and products. Must any of these structures contain atoms with fewer than eight valence electrons?

Madi Sousa

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Problem 107

Which of the following chlorine oxides are odd-electron molecules? (a) $\mathrm{Cl}_{2} \mathrm{O}_{7} ;$ (b) $\mathrm{Cl}_{2} \mathrm{O}_{6} ;$ (c) $\mathrm{ClO}_{4} ;$ (d) $\mathrm{ClO}_{3}$
(e) $\mathrm{ClO}_{2}$.

Sam Limsuwannarot

Sam Limsuwannarot

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Problem 108

Which of the following nitrogen oxides are odd-electron molecules? (a) $\mathrm{NO} ;$ (b) $\mathrm{NO}_{2} ;$ (c) $\mathrm{NO}_{3} ;$ (d) $\mathrm{N}_{2} \mathrm{O}_{4} ;$ (e) $\mathrm{N}_{2} \mathrm{O}_{5}$.

Sam Limsuwannarot

Sam Limsuwannarot

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Problem 109

Which of the Lewis structures in Figure P8.109 contributes most to the bonding in CNO?

Madi Sousa

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Problem 110

Why is the Lewis structure in Figure P8.110 unlikely to contribute much to the bonding in NCO?

Jorge Villanueva

Jorge Villanueva

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Problem 111

Using Lewis structures, explain why dimethylaluminum chloride is more likely to exist as $\left(\mathrm{CH}_{3}\right)_{4} \mathrm{Al}_{2} \mathrm{Cl}_{2}$ than as $\left(\mathrm{CH}_{3}\right)_{2} \mathrm{AlCl}$.

Sam Limsuwannarot

Sam Limsuwannarot

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Problem 112

When left at room temperature, mixtures of $\mathrm{BF}_{3}$ and $\mathrm{BCl}_{3}$ are found to contain significant amounts of $\mathrm{BF}_{2} \mathrm{Cl}$ and BFCl $_{2} .$ Using Lewis structures, explain the origin of the latter two compounds..

Sam Limsuwannarot

Sam Limsuwannarot

Numerade Educator

Problem 113

Some have argued that $\mathrm{SF}_{6}$ has ionic resonance forms that do not require an expanded octet for S. Draw a resonance structure consistent with this hypothesis and assign formal charges to each atom. Is this resonance form better than or the same as the one with an expanded octet?

Sam Limsuwannarot

Sam Limsuwannarot

Numerade Educator

Problem 114

The synthesis of an extremely unusual molecule, $[\mathrm{NO}]_{2}+\left[\mathrm{XeF}_{8}\right]^{2-},$ was reported close to 50 years ago. The structure of $\left[\mathrm{XeF}_{8}\right]^{2-}$ shows that all eight fluorine atoms are within bonding distance of the Xe. Draw a Lewis structure for the $\left[\mathrm{XeF}_{8}\right]^{2-}$ anion.

Sam Limsuwannarot

Sam Limsuwannarot

Numerade Educator

Problem 115

Do you expect the nitrogen-oxygen bond length in the nitrate ion to be the same as in the nitrite ion? Explain.

Sam Limsuwannarot

Sam Limsuwannarot

Numerade Educator

Problem 116

Why is the oxygen-oxygen bond length in $\mathrm{O}_{3}$ not the same
as in $\mathrm{O}_{2} ?$

Sam Limsuwannarot

Sam Limsuwannarot

Numerade Educator

Problem 117

Explain why the nitrogen-oxygen bond lengths in $\mathrm{N}_{2} \mathrm{O}_{4}$ (which has a nitrogen-nitrogen bond) and $\mathrm{N}_{2} \mathrm{O}$ are nearly identical ( 118 and 119 pm, respectively).

Sam Limsuwannarot

Sam Limsuwannarot

Numerade Educator

Problem 118

Do you expect the sulfur-oxygen bond lengths in $\mathrm{SO}_{3}^{2-}$ and $\mathrm{SO}_{4}^{2-}$ ions to be about the same? Why?

Sam Limsuwannarot

Sam Limsuwannarot

Numerade Educator

Problem 119

Rank the following ions in order of (a) increasing nitrogenoxygen bond lengths and (b) increasing bond energies:
$\mathrm{NO}_{2}^{-} ; \mathrm{NO}^{+} ; \mathrm{NO}_{3}^{-}$.

Sam Limsuwannarot

Sam Limsuwannarot

Numerade Educator

Problem 120

Rank the following compounds and ions in order of
(a) increasing carbon-oxygen bond lengths and
(b) increasing bond energies: $\mathrm{CO} ; \mathrm{CO}_{2} ; \mathrm{CO}_{3}^{2-}$.

Sam Limsuwannarot

Sam Limsuwannarot

Numerade Educator

Problem 121

Do you expect the boron-fluorine bond energy to be the same in $\mathrm{BF}_{3}$ and $\mathrm{F}_{3} \mathrm{BNH}_{3} ?$

Sam Limsuwannarot

Sam Limsuwannarot

Numerade Educator

Problem 122

The boron-oxygen distances in the $\mathrm{BO}_{2}^{+}$ cation are equal. Does this mean the bond order of the $\mathrm{B}$ -O bond is two? Explain.

Sam Limsuwannarot

Sam Limsuwannarot

Numerade Educator

Problem 123

Why must the stoichiometry of a reaction be known in order to estimate the enthalpy change from bond energies?

Sam Limsuwannarot

Sam Limsuwannarot

Numerade Educator

Problem 124

Why must the structures of the reactants and products be known in order to estimate the enthalpy change of a reaction from bond energies?

Sam Limsuwannarot

Sam Limsuwannarot

Numerade Educator

Problem 125

When calculating the enthalpy change for a chemical reaction by using bond energies, why is it important to know the phase (solid, liquid, or gaseous) for every compound in the reaction?

Sam Limsuwannarot

Sam Limsuwannarot

Numerade Educator

Problem 126

If the energy needed to break 2 moles of $\mathrm{C}=\mathrm{O}$ bonds is greater than the sum of the energies needed to break the $\mathrm{O}=\mathrm{O}$ bonds in 1 mole of $\mathrm{O}_{2}$ and vaporize 1 mole of carbon, why does the combustion of pure carbon release heat?

Sam Limsuwannarot

Sam Limsuwannarot

Numerade Educator

Problem 127

Use average bond energies to estimate the enthalpy changes of the following reactions:
a. $\mathrm{N}_{2}(g)+3 \mathrm{H}_{2}(g) \rightarrow 2 \mathrm{NH}_{3}(g)$
b. $\mathrm{N}_{2}(g)+2 \mathrm{H}_{2}(g) \rightarrow \mathrm{H}_{2} \mathrm{NNH}_{2}(g)$
c. $2 \mathrm{N}_{2}(g)+\mathrm{O}_{2}(g) \rightarrow 2 \mathrm{N}_{2} \mathrm{O}(g)$

Madi Sousa

Numerade Educator

Problem 128

Use average bond energies to estimate the enthalpy changes of the following reactions:
a. $\mathrm{CO}_{2}(g)+\mathrm{H}_{2}(g) \rightarrow \mathrm{H}_{2} \mathrm{O}(g)+\mathrm{CO}(g)$
b. $\mathrm{N}_{2}(g)+\mathrm{O}_{2}(g) \rightarrow 2 \mathrm{NO}(g)$
c.$\mathrm{C}(s)+\mathrm{CO}_{2}(g) \rightarrow 2 \mathrm{CO}(g)$

Madi Sousa

Numerade Educator

Problem 129

The combustion of $\mathrm{CO}$ to $\mathrm{CO}_{2}$ releases $283 \mathrm{kJ} / \mathrm{mol}$. What is the bond energy of the carbon-oxygen bond in carbon monoxide?

Sam Limsuwannarot

Sam Limsuwannarot

Numerade Educator

Problem 130

Use average bond energies to estimate the standard enthalpy of formation of HF gas.

Madi Sousa

Numerade Educator

Problem 131

Estimate how much less energy is released during the incomplete combustion of 1 mole of methane to carbon monoxide and water vapor than in the complete combustion to carbon dioxide and water vapor.

Madi Sousa

Numerade Educator

Problem 132

Estimate how much more energy is released by the reaction
$$\mathrm{C}(s)+\mathrm{O}_{2}(g) \rightarrow \mathrm{CO}_{2}(g)$$
than by the reaction
$$\mathrm{C}(s)+\frac{1}{2} \mathrm{O}_{2}(g) \rightarrow \mathrm{CO}(g)$$

Sam Limsuwannarot

Sam Limsuwannarot

Numerade Educator

Problem 133

Estimate $\Delta H_{\mathrm{rxn}}$ for the following reaction:
$$4 \mathrm{NH}_{3}(g)+7 \mathrm{O}_{2}(g) \rightarrow 4 \mathrm{NO}_{2}(g)+6 \mathrm{H}_{2} \mathrm{O}(g)$$

Madi Sousa

Numerade Educator

Problem 134

The value of $\Delta H_{\mathrm{rxn}}$ for the reaction
$$2 \mathrm{H}_{2} \mathrm{S}(g)+3 \mathrm{O}_{2}(g) \rightarrow 2 \mathrm{SO}_{2}(g)+2 \mathrm{H}_{2} \mathrm{O}(g)$$
is $-1036 \mathrm{kJ} .$ Estimate the energy of the bonds in $\mathrm{SO}_{2}$

Madi Sousa

Numerade Educator

Problem 135

A molecular view of the combustion of $\mathrm{CS}_{2}$ is shown in Figure $P 8.135 .$ If the standard enthalpy of combustion of $\mathrm{CS}_{2}$ is $-1102 \mathrm{kJ} / \mathrm{mol},$ what is the average bond energy for the carbon-sulfur bonds in $\mathrm{CS}_{2} ?$
CAN'T COPY THE FIGURE

Madi Sousa

Numerade Educator

Problem 136

The standard enthalpy of reaction for the decomposition of carbon oxysulfide (COS) to $\mathrm{CO}_{2}$ and $\mathrm{CS}_{2}$, as shown in Figure $\mathrm{P} 8.136,$ is $-1.9 \mathrm{kJ} / \mathrm{mol} .$ Are the apparent bond energies of the carbon-sulfur and carbon-oxygen bonds in COS stronger or weaker than in $\mathrm{CS}_{2}$ and $\mathrm{CO}_{2}$, respectively?

Madi Sousa

Numerade Educator

Problem 137

Carbon and oxygen form three oxides: $\mathrm{CO}, \mathrm{CO}_{2},$ and carbon suboxide $\left(\mathrm{C}_{3} \mathrm{O}_{2}\right) .$ Draw a Lewis structure for $\mathrm{C}_{3} \mathrm{O}_{2}$ in which the three carbon atoms are bonded to each other, and predict whether the carbon-oxygen bond lengths in the carbon suboxide molecule are equal.

Sam Limsuwannarot

Sam Limsuwannarot

Numerade Educator

Problem 138

Spectroscopic analysis of the linear molecule $\mathrm{N}_{4} \mathrm{O}$ reveals that the nitrogen-oxygen bond length is $135 \mathrm{pm}$ and that there are three nitrogen-nitrogen bond lengths: 148,127 and $115 \mathrm{pm} .$ Draw the Lewis structure for $\mathrm{N}_{4} \mathrm{O}$ consistent with these observations.

Sam Limsuwannarot

Sam Limsuwannarot

Numerade Educator

Problem 139

The unpaired dots in Lewis symbols of the elements represent valence electrons available for covalent bond formation. In Figure P8.139, which of the options for placing dots around the symbol for each element is preferred?

Madi Sousa

Numerade Educator

Problem 140

On the basis of the Lewis symbols in Figure P8.140, predict to which group in the periodic table element X belongs.

Madi Sousa

Numerade Educator

Problem 141

Use formal charges to predict whether the atoms in carbon disulfide are arranged CSS or SCS.

Sam Limsuwannarot

Sam Limsuwannarot

Numerade Educator

Problem 142

The following is a family of weak acids: $\mathrm{HClO}, \mathrm{HClO}_{2}$ and HClO $_{3} .$ Draw their Lewis structures, using formal charges to predict the best arrangement of atoms. Show any resonance forms of the molecules.

Sam Limsuwannarot

Sam Limsuwannarot

Numerade Educator

Problem 143

Chemical Weapons Phosgene is a poisonous gas first used in chemical warfare during World War I. It has the formula $\mathrm{COCl}_{2}(\mathrm{C}$ is the central atom).
a. Draw its Lewis structure.
b. Phosgene kills because it reacts with water in nasal passages, in the lungs, and on the skin to produce carbon dioxide and hydrogen chloride. Write a balanced chemical equation for this process, showing the Lewis structures for reactants and products.

Madi Sousa

Numerade Educator

Problem 144

The dinitramide anion $\left[\mathrm{N}\left(\mathrm{NO}_{2}\right)_{2}^{-}\right]$ was first isolated in
1996. The arrangement of atoms in $\mathrm{N}\left(\mathrm{NO}_{2}\right)_{2}^{-}$ is shown in Figure P8.144.
a. Complete the Lewis structure for $\mathrm{N}\left(\mathrm{NO}_{2}\right)_{2}$, including any resonance forms, and assign formal charges.
b. Explain why the nitrogen-oxygen bond lengths in $\mathrm{N}\left(\mathrm{NO}_{2}\right)_{2}^{-}$ and $\mathrm{N}_{2} \mathrm{O}$ should (or should not) be similar.
c. $\mathrm{N}\left(\mathrm{NO}_{2}\right)_{2}^{-}$ was isolated as $\left[\mathrm{NH}_{4}^{+}\right]\left[\mathrm{N}\left(\mathrm{NO}_{2}\right)_{2}^{-}\right] .$ Draw
the Lewis structure for $\mathrm{NH}_{4}^{+}$.

Jorge Villanueva

Jorge Villanueva

Numerade Educator

Problem 145

Silver cyanate (AgOCN) is a source of the cyanate ion $\left(\mathrm{OCN}^{-}\right),$ which reacts with several small molecules. Under certain conditions the species OCN is an anion with a charge of $1-;$ under other conditions it is a neutral, odd-electron molecule.
a. Two molecules of OCN combine to form OCNNCO. Draw the Lewis structures for this molecule, including
all resonance forms.
b. The OCN" ion reacts with BrNO, forming the unstable molecule OCNNO. Draw the Lewis structures for BrNO and OCNNO, including all resonance forms.
c. The OCN- ion reacts with $\mathrm{Br}_{2}$ and $\mathrm{NO}_{2}$ to produce $\mathrm{N}_{2} \mathrm{O}, \mathrm{CO}_{2}, \mathrm{BrNCO},$ and $\mathrm{OCN}(\mathrm{CO}) \mathrm{NCO} .$ Draw three
of the resonance forms of $\mathrm{OCN}(\mathrm{CO}) \mathrm{NCO},$ which has the arrangement of atoms shown in Figure P8.145.

Jorge Villanueva

Jorge Villanueva

Numerade Educator

Problem 146

During the reaction of the cyanate ion $\left(\mathrm{OCN}^{-}\right)$ with $\mathrm{Br}_{2}$ and $\mathrm{NO}_{2},$ a very unstable substance called an intermediate forms and then quickly falls apart. Its formula is $\mathrm{O}_{2} \mathrm{NNCO}$
a. Draw three of the resonance forms for $\mathrm{O}_{2} \mathrm{NNCO}$, assign formal charges, and predict which of the three contributes the most to the bonding in $\mathrm{O}_{2} \mathrm{NNCO}$. The connectivity of the atoms is shown in Figure $\mathrm{P} 8.146(\mathrm{a})$
b. Which bond in $\mathrm{O}_{2} \mathrm{NNCO}$ must break in the reaction with $\mathrm{Br}_{2}$ to form BrNCO? What other product forms?
c. Draw Lewis structures for a different arrangement of the $\mathrm{N}, \mathrm{C},$ and $\mathrm{O}$ atoms in $\mathrm{O}_{2} \mathrm{NNCO}$ as shown in Figure $P 8.146(b)$.

Madi Sousa

Numerade Educator

Problem 147

A compound with the formula $\mathrm{Cl}_{2} \mathrm{O}_{6}$ decomposes to a mixture of $\mathrm{ClO}_{2}$ and $\mathrm{ClO}_{4} .$ Draw two Lewis structures for $\mathrm{Cl}_{2} \mathrm{O}_{6}:$ one with a chlorine-chlorine bond and one with a Cl- $\mathrm{O}-$ Cl arrangement of atoms. Draw a Lewis structure for $\mathrm{ClO}_{2}$
$$\mathrm{Cl}_{2} \mathrm{O}_{6} \rightarrow \mathrm{ClO}_{2}+\mathrm{ClO}_{4}$$

Sam Limsuwannarot

Sam Limsuwannarot

Numerade Educator

Problem 148

A compound consisting of chlorine and oxygen, $\mathrm{Cl}_{2} \mathrm{O}_{7}$ decomposes by the following reaction:
$$
\mathrm{Cl}_{2} \mathrm{O}_{7} \rightarrow \mathrm{ClO}_{4}+\mathrm{ClO}_{3}
$$
a. Draw two Lewis structures for $\mathrm{Cl}_{2} \mathrm{O}_{7}$ : one with a chlorine-chlorine bond and one with a $\mathrm{Cl}-\mathrm{O}-\mathrm{Cl}$ arrangement of atoms.
b. Draw a Lewis structure for $\mathrm{ClO}_{3}$

Sam Limsuwannarot

Sam Limsuwannarot

Numerade Educator

Problem 149

The odd-electron molecule CN dimerizes to give cyanogen $\left(\mathrm{C}_{2} \mathrm{N}_{2}\right)$
a. Draw a Lewis structure for $\mathrm{CN}$, and predict which arrangement for cyanogen is more likely: NCCN or CNNC.
b. Cyanogen reacts slowly with water to produce oxalic acid $\left(\mathrm{H}_{2} \mathrm{C}_{2} \mathrm{O}_{4}\right)$ and ammonia; the Lewis structure for oxalic acid is shown in Figure P8.149. Compare this structure with your answer in part (a). When the actual structures of molecules have been defined experimentally, the structures have been used to refine Lewis structures. Does this structure increase your confidence that the structure you selected in part
(a) may be the better one?

Madi Sousa

Numerade Educator

Problem 150

Draw all resonance forms for the molecules NSF and HBS where $S$ and $B$ are the central atoms, respectively. Include possible ionic structures for NSF.

DD

David Dick

Numerade Educator

Problem 151

The molecular structure of sulfur cyanide trifluoride $\left(\mathrm{SF}_{3} \mathrm{CN}\right)$ has been shown to have the arrangement of atoms with the indicated bond lengths in Figure P8.151. Complete the Lewis structure for $\mathrm{SF}_{3} \mathrm{CN}$, and assign formal charges.

Sam Limsuwannarot

Sam Limsuwannarot

Numerade Educator

Problem 152

Strike-Anywhere Matches Heating phosphorus with sulfur gives $P_{4} S_{3},$ a solid used in the heads of strike-anywhere matches (Figure $\mathrm{P} 8.152$ ). $\mathrm{P}_{4} \mathrm{S}_{3}$ has the Lewis structure framework shown. Complete the Lewis structure so that each atom has the optimum formal charge.

Sam Limsuwannarot

Sam Limsuwannarot

Numerade Educator

Problem 153

The heavier group 16 elements can expand their valence shell. The $\mathrm{TeOF}_{6}^{2-}$ anion was first prepared in $1993 .$ Draw the Lewis structure for $\operatorname{Te} \mathrm{OF}_{6}^{2-}$.

Sam Limsuwannarot

Sam Limsuwannarot

Numerade Educator

Problem 154

Sulfur in the Environment Sulfur is cycled in the environment through compounds such as dimethyl sulfide $\left(\mathrm{CH}_{3} \mathrm{SCH}_{3}\right),$ hydrogen sulfide $\left(\mathrm{H}_{2} \mathrm{S}\right),$ and sulfite and sulfate ions. Draw Lewis structures for these four species. Are expanded valence shells needed to minimize the formal charges for any of these species?

Jorge Villanueva

Jorge Villanueva

Numerade Educator

Problem 155

How many pairs of electrons does xenon share in the following molecules and ions? (a) $\mathrm{XeF}_{2} ;$ (b) $\mathrm{XeOF}_{2}$
(c) $\mathrm{XeF}^{+} ;$ (d) $\mathrm{XeF}_{5}^{+} ;$ (e) $\mathrm{XeO}_{4}$.

Sam Limsuwannarot

Sam Limsuwannarot

Numerade Educator

Problem 156

Consider a hypothetical structure of ozone that is cyclic (the atoms form a ring) such that its three O atoms are at the corners of a triangle. Draw the Lewis structure for this molecule.

Sam Limsuwannarot

Sam Limsuwannarot

Numerade Educator

Problem 157

Bond lengths and electrostatic potential mapping provide experimental evidence about covalent bonds present in
a molecule. Which of these would help characterize the bonding in a compound with the formula $\mathrm{A}_{2} \mathrm{X}$ in terms of the following?
a. distinguishing between these two bonding patterns:
$\mathrm{X}-\mathrm{A}-\mathrm{A}$ and $\mathrm{A}-\mathrm{X}-\mathrm{A}$
b. distinguishing between these resonance forms:
$\mathrm{A}-\mathrm{X} \equiv \mathrm{A}, \mathrm{A}=\mathrm{X}=\mathrm{A},$ and $\mathrm{A} \equiv \mathrm{X}-\mathrm{A}$

Sam Limsuwannarot

Sam Limsuwannarot

Numerade Educator

Problem 158

Explosive Cation The highly explosive $\mathrm{N}_{5}^{+}$ cation was first isolated in 1999 by reaction of $\mathrm{N}_{2} \mathrm{F}^{+}$ with $\mathrm{HN}_{3}:$
$$
\mathrm{N}_{2} \mathrm{F}^{+}+\mathrm{HN}_{3} \rightarrow \mathrm{N}_{5}^{+}+\mathrm{HF}
$$
Draw the Lewis structures for the reactants and products, including all resonance forms.

Madi Sousa

Numerade Educator

Problem 159

Jupiter's Atmosphere The ionic compound NH_4 SH was detected in the atmosphere of Jupiter (Figure P8.159) by the Galileo space probe in $1995 .$ Draw the Lewis structure for $\mathrm{NH}_{4} \mathrm{SH}$. Why couldn't there be a covalent bond between the nitrogen and sulfur atoms, making $\mathrm{NH}_{4} \mathrm{SH}$ a molecular compound?

Madi Sousa

Numerade Educator

Problem 160

Antacid Tablets Antacids commonly contain calcium carbonate, magnesium hydroxide, or both. Draw the Lewis structures for calcium carbonate and magnesium hydroxide.

Sam Limsuwannarot

Sam Limsuwannarot

Numerade Educator

Problem 161

An allotrope of nitrogen, $\mathrm{N}_{4},$ was reported in $2002 .$ The compound has a lifetime of $1 \mu \mathrm{s}$ at $298 \mathrm{K}$ and was prepared by adding an electron to $\mathrm{N}_{4}^{+}$. Because the compound cannot be isolated, its structure is unconfirmed experimentally.
a. Draw the Lewis structures for all the resonance forms of linear $\mathrm{N}_{4}$. (Linear means that all four nitrogens are in
a straight line.)
b. Assign formal charges, and determine which structure is the best description of $\mathrm{N}_{4}$
c. Draw a Lewis structure for a ring (cyclic) form of $\mathrm{N}_{4}$ and assign formal charges.

Madi Sousa

Numerade Educator

Problem 162

Scientists have predicted the existence of $\mathrm{O}_{4}$ even though this compound has never been observed. However, $\mathrm{O}_{4}^{2-}$ has been detected. Draw the Lewis structures for $\mathrm{O}_{4}$ and $\mathrm{O}_{4}^{2-}$.

Sam Limsuwannarot

Sam Limsuwannarot

Numerade Educator

Problem 163

Draw a Lewis structure for AlFCl,, the second product in the synthesis of $\mathrm{Cl}_{2} \mathrm{O}_{2}$ in the following reaction:
$$\mathrm{FClO}_{2}(g)+\mathrm{AlCl}_{3}(s) \rightarrow \mathrm{Cl}_{2} \mathrm{O}_{2}(g)+\mathrm{AlFCl}_{2}(s)$$

Ronald Prasad

Numerade Educator

Problem 164

Draw Lewis structures for $\mathrm{BF}_{3}$ and $\left(\mathrm{CH}_{3}\right)_{2} \mathrm{BF}$. The $\mathrm{B}-\mathrm{F}$ distance in both molecules is the same $(130 \mathrm{pm}) .$ Does this observation support the argument that all the boronfluorine bonds in $\mathrm{BF}_{3}$ are single bonds?

Sam Limsuwannarot

Sam Limsuwannarot

Numerade Educator

Problem 165

Which of the following molecules and ions contains an atom with an expanded valence shell? (a) $\mathrm{Cl}_{2} ;$ (b) $\mathrm{ClF}_{3}$ (c) $\mathrm{ClI}_{3} ;$ (d) $\mathrm{ClO}^{-}$.

Madi Sousa

Numerade Educator

Problem 166

Which of the following molecules contains an atom with an expanded valence shell? (a) $\mathrm{XeF}_{2} ;$ (b) $\mathrm{GaCl}_{3} ;$ (c) $\mathrm{ONF}_{3}$ (d) $\mathrm{SeO}_{2} \mathrm{F}_{2}$.

Jorge Villanueva

Jorge Villanueva

Numerade Educator

Problem 167

A linear nitrogen anion, $\mathrm{N}_{5}$, was isolated for the first time in 1999
a. Draw the Lewis structures for four resonance forms of linear $\mathrm{N}_{5}^{-}$
b. Assign formal charges to the atoms in the structures in part (a), and identify the structures that contribute the most to the bonding in $\mathrm{N}_{5}^{-}$.
c. Compare the Lewis structures for $\mathrm{N}_{5}^{-}$ and $\mathrm{N}_{3}^{-} .$ In which ion do the nitrogen-nitrogen bonds have the higher average bond order?

Ronald Prasad

Numerade Educator

Problem 168

Carbon tetroxide $\left(\mathrm{CO}_{4}\right)$ was discovered in 2003
a. The four atoms in $\mathrm{CO}_{4}$ are predicted to be arranged as shown in Figure P8.168. Complete the Lewis structure for $\mathrm{CO}_{4}$
b. Are there any resonance forms for the structure you drew that have zero formal charges on all atoms?
c. Can you draw a structure in which all four oxygen atoms in $\mathrm{CO}_{4}$ are bonded to carbon?

Madi Sousa

Numerade Educator

Problem 169

Plot the electronegativities of elements with $Z=3$ to 9 (y-axis) versus their first ionization energy ( $x$ -axis). Is the plot linear? Use your graph to predict the electronegativity of neon, whose first ionization energy is $2080 \mathrm{kJ} / \mathrm{mol}$.

Madi Sousa

Numerade Educator

Problem 170

Use the data in Figures 7.39 and 8.6 to plot electronegativity as a function of first ionization energy for the main group elements of the fifth row of the periodic table. From this plot estimate the electronegativity of xenon, whose first ionization energy is $1170 \mathrm{kJ} / \mathrm{mol}$.

Madi Sousa

Numerade Educator

Problem 171

The cation $\mathrm{N}_{2} \mathrm{F}^{+}$ is isoelectronic with $\mathrm{N}_{2} \mathrm{O}$.
a. What does it mean to be isoelectronic?
b. Draw the Lewis structure for $\mathrm{N}_{2} \mathrm{F}^{+}$. (Hint: The molecule contains a nitrogen-nitrogen bond.)
c. Which atom has the +1 formal charge in the structure you drew in part (b)?
d. Does $\mathrm{N}_{2} \mathrm{F}^{+}$ have resonance forms?
e. Could the middle atom in the $\mathrm{N}_{2} \mathrm{F}^{+}$ ion be a fluorine atom? Explain your answer.

Sam Limsuwannarot

Sam Limsuwannarot

Numerade Educator

Problem 172

Ozone Depletion Methyl bromide (CH $_{3} \mathrm{Br}$ ) is produced naturally by fungi. Methyl bromide has also been used in agriculture as a fumigant, but this use is being phased out because the compound has been linked to ozone depletion in the upper atmosphere.
a. Draw the Lewis structure for $\mathrm{CH}_{3} \mathrm{Br}$.
b. Which bond in $\mathrm{CH}_{3} \mathrm{Br}$ is more polar, carbon-hydrogen
or carbon-bromine?

Sam Limsuwannarot

Sam Limsuwannarot

Numerade Educator

Problem 173

All the carbon-fluorine bonds in tetrafluoroethylenc (Figure $\mathrm{P} 8.173$ ) are polar, but experimental results show that the molecule as a whole is nonpolar. Draw arrows on each bond to show the direction of polarity, and suggest a reason why the molecule is nonpolar.

Sam Limsuwannarot

Sam Limsuwannarot

Numerade Educator

Problem 174

Atoms of Xe have complete octets, yet the compound $\mathrm{XeO}_{2}$ exists. How is this possible?

Sam Limsuwannarot

Sam Limsuwannarot

Numerade Educator

Problem 175

Free radicals increase in stability, and hence decrease in reactivity, if they have more than one atom in their structure that can carry the unpaired electron.
a. Draw Lewis structures for the three free radicals formed from $\mathrm{CF}_{2} \mathrm{Cl}_{2}$ in the stratosphere $-\mathrm{ClO}, \mathrm{Cl},$ and $\mathrm{CF}_{2} \mathrm{Cl}-$ and use this principle to rank them in order of reactivity.
b. Free radicals are "neutralized" when they react with each other, forming an electron pair (a single covalent bond) between two atoms. This is called a termination reaction because it shuts down any reaction that was powered by the free radical. Predict the formula of the molecules that are produced when the chlorine free radical reacts with each of the free radicals in part (a).

Madi Sousa

Numerade Educator