Solved: Using the molecular orbital energy ordering for second-row homonuclear diatomic

Determine the electron geometry, molecular geometry, and idealized bond angles for each molecule. In which cases do you expect deviations from the idealized bond angle? a. PF3 b. SBr2 c. CHCl3 d. CS2

Determine the electron geometry, molecular geometry, and idealized bond angles for each molecule. In which cases do you expect deviations from the idealized bond angle? a. CF4 b. NF3 c. OF2 d. H2S

Which species has the smaller bond angle, H3O+ or H2O? Explain.

Which species has the smaller bond angle, ClO4- or ClO3-? Explain.

Determine the molecular geometry and sketch each molecule or ion using the bond conventions shown in the “Representing Molecular Geometries on Paper” box in Section 10.4. a. SF4 b. CIF3 c. IF2- d. IBr4-

Determine the molecular geometry and sketch each molecule or ion, using the bond conventions shown in the "Representing Molecular Geometries on Paper" Box in Section 10.4. a. BrF5 b. SCl6 c. PF5 d. IF4+

Determine the molecular geometry about each interior atom and sketch each molecule. a. C2H2 (skeletal structure HCCH) b. C2H4 (skeletal structure H2CCH2) c. C2H6 (skeletal structure H3CCH3)

Determine the molecular geometry about each interior atom and sketch each molecule. a. N2 b. N2H2 (skeletal structure HNNH) c. N2H4 (skeletal structure H2NNH2)

Each ball-and-stick model shows the electron and molecular geometry of a generic molecule. Explain what is wrong with each molecular geometry and provide the correct molecular geometry, given the number of lone pairs and bonding groups on the central atom.

Each ball-and-stick model shows the electron and molecular geometry of a generic molecule. Explain what is wrong with each molecular geometry and provide the correct molecular geometry, given the number of lone pairs and bonding groups on the central atom.

Determine the geometry about each interior atom in each molecule and sketch the molecule. (Skeletal structure is indicated in parentheses.) a. CH3OH ( H3COH ) b. CH3OCH3 ( H3COCH3 ) c. H2O2 (HOOH)

Determine the geometry about each interior atom in each molecule and sketch the molecule. (Skeletal structure is indicated in parentheses.) a. CH3NH2 ( H3CNH2 ) b. CH3CO2CH3 ( H3CCOOCH3 both O atoms attached to second C) c. NH2CO2H ( H2NCOOH both O atoms attached to C)

Explain why CO2 and CCl4 are both nonpolar even though they contain polar bonds.

CH3F is a polar molecule, even though the tetrahedral geometry often leads to nonpolar molecules. Explain.

Determine whether each molecule in Exercise 35 is polar or nonpolar.

Determine whether each molecule in Exercise 36 is polar or nonpolar.

Determine whether each molecule is polar or nonpolar. a. ClO3- b. SCl22 c. SCl4 d. BrCl5

The valence electron configurations of several atoms are shown next. How many bonds can each atom make without hybridization? a. Be 2s2 b. P 3s23p3 c. F 2s22p5

The valence electron configurations of several atoms are shown next. How many bonds can each atom make without hybridization? a. B 2s22p1 b. N 2s22p3 c. O 2s22p4

Write orbital diagrams (boxes with arrows in them) to represent the electron configurations—without hybridization—for all the atoms in PH3. Circle the electrons involved in bonding. Draw a three-dimensional sketch of the molecule and show orbital overlap. What bond angle do you expect from the unhybridized orbitals? How well does valence bond theory agree with the experimentally measured bond angle of 93.3o?

Write orbital diagrams (boxes with arrows in them) to represent the electron configurations—without hybridization—for all the atoms in SF2. Circle the electrons involved in bonding. Draw a three-dimensional sketch of the molecule and show orbital overlap. What bond angle do you expect from the unhybridized orbitals? How well does valence bond theory agree with the experimentally measured bond angle of 98.2o?

Write orbital diagrams (boxes with arrows in them) to represent the electron configuration of carbon before and after sp3 hybridization.

Problem 58E Write orbital diagrams (boxes with arrows in them) to represent the electron configurations of carbon before and after sp hybridization.

Which hybridization scheme allows the formation of at least one bond?

For each molecular geometry, list the number of total electron groups, the number of bonding groups, and the number of lone pairs on the central atom.

For each molecular geometry, list the number of total electron groups, the number of bonding groups, and the number of lone pairs on the central atom.

A molecule with the formula AB3 has a trigonal planar geometry. How many electron groups are on the central atom?

A molecule with the formula AB3 has a trigonal pyramidal geometry. How many electron groups are on the central atom (A)?

Problem 30E Write a short paragraph describing chemical bonding according to the Lewis model, valence bond theory, and molecular orbital theory. Indicate how the theories differ in their description of a chemical bond and indicate the strengths and weaknesses of each theory. Which theory is correct?

Problem 29E In molecular orbital theory, what is a nonbonding orbital?

Why does the energy ordering of the molecular orbitals of the period 2 diatomic molecules change in going from N2 to O2?

Problem 27E Explain the difference between a paramagnetic species and a diamagnetic one.

Draw an energy diagram for the molecular orbitals of period 2 diatomic molecules. Show the difference in ordering for B2, C2, and N2 compared to O2, F2, and Ne2.

Sketch each molecular orbital.

Problem 23E How is the number of molecular orbitals approximated by a linear combination of atomic orbitals related to the number of atomic orbitals used in the approximation?

Problem 22E In molecular orbital theory, what is bond order? Why is it important?

Problem 21E What is the role of wave interference in determining whether a molecular orbital is bonding or antibonding?

Problem 20E What is an antibonding molecular orbital?

Problem 19E What is a bonding molecular orbital?

Problem 18E Explain the difference between hybrid atomic orbitals in valence bond theory and LCAO molecular orbitals in molecular orbital theory.

Problem 17E What is a chemical bond according to molecular orbital theory?

Problem 16E Name the hybridization scheme that corresponds to each electron geometry: a. linear b. trigonal planar c. tetrahedral d. trigonal Oipyramidal e. Octahedral

Problem 15E In the Lewis model, the two bonds in a double bond look identical. However, valence bond theory shows that they are not. Describe a double bond according to valence bond theory. Explain why rotation is restricted about a double bond, but not about a single bond.

Sketch each hybrid orbital: a. sp b. sp2 c. sp3 d. sp3d e. sp3d2

Problem 13E How is the number of hybrid orbitals related to the number of standard atomic orbitals that are hybridized?

Describe the geometry around each of the three central atoms in the CH3COOH molecule

Which of the following species are tetrahedral? SiCl4, SeF4, XeF4, CI4, CdCl4

Define dipole moment. What are the units and symbol for dipole moment?

What is the relationship between the dipole moment and the bond moment? How is it possible for a molecule to have bond moments and yet be nonpolar?

Explain why an atom cannot have a permanent dipole moment.

The bonds in beryllium hydride (BeH2) molecules are polar, and yet the dipole moment of the molecule is zero. Explain.

Referring to Table 10.3, arrange the following molecules in order of increasing dipole moment: H2O, H2S, H2Te, H2Se.

The dipole moments of the hydrogen halides decrease from HF to HI (see Table 10.3). Explain this trend.

List the following molecules in order of increasing dipole moment: H2O, CBr4, H2S, HF, NH3, CO2.

Does the molecule OCS have a higher or lower dipole moment than CS2?

Which of the following molecules has a higher dipole moment? (a) (b) CPC CPC Br G H D D Br G H Br G H D D H G B

Arrange the following compounds in order of increasing dipole moment: E Cl Cl H Cl A A Cl Cl A A Cl ECl Cl A A Cl E Cl Cl H (a) (b) (c) (d)

What is valence bond theory? How does it differ from the Lewis concept of chemical bonding?

Use valence bond theory to explain the bonding in Cl2 and HCl. Show how the atomic orbitals overlap when a bond is formed

Draw a potential energy curve for the bond formation in F2

(a) What is the hybridization of atomic orbitals? Why is it impossible for an isolated atom to exist in the hybridized state? (b) How does a hybrid orbital differ from a pure atomic orbital? Can two 2p orbitals of an atom hybridize to give two hybridized orbitals?

What is the angle between the following two hybrid orbitals on the same atom? (a) sp and sp hybrid orbitals, (b) sp2 and sp2 hybrid orbitals, (c) sp3 and sp3 hybrid orbitals

How would you distinguish between a sigma bond and a pi bond?

Describe the bonding scheme of the AsH3 molecule in terms of hybridization.

What is the hybridization state of Si in SiH4 and in H3SiSiH3?

Describe the change in hybridization (if any) of the Al atom in the following reaction: AlCl3 1 Cl2 AlCl2 4

Consider the reaction BF3 1 NH3 F3BNH3 Describe the changes in hybridization (if any) of the B and N atoms as a result of this reaction.

What hybrid orbitals are used by nitrogen atoms in the following species? (a) NH3, (b) H2NNH2, (c) NO3 2

What are the hybrid orbitals of the carbon atoms in the following molecules? (a) H3CCH3 (b) H3CCHCH2 (c) CH3CCCH2OH (d) CH3CHO (e) CH3COOH

Specify which hybrid orbitals are used by carbon atoms in the following species: (a) CO, (b) CO2, (c) CN2.

What is the hybridization state of the central N atom in the azide ion, N3 2? (Arrangement of atoms: NNN.)

The allene molecule H2CCCH2 is linear (the three C atoms lie on a straight line). What are the hybridization states of the carbon atoms? Draw diagrams to show the formation of sigma bonds and pi bonds in allene.

Describe the hybridization of phosphorus in PF5.

How many sigma bonds and pi bonds are there in each of the following molecules? A H H A (a) (b) (c) CPC H A A H H3COCPCOCqCOH DCl G H H G H D ClOCOCl

How many pi bonds and sigma bonds are there in the tetracyanoethylene molecule? CPC DCqN G CqN NqCG NqC D

Give the formula of a cation comprised of iodine and fluorine in which the iodine atom is sp3 d- hybridized.

Give the formula of an anion comprised of iodine and fluorine in which the iodine atom is sp3 d2 - hybridized.

What is molecular orbital theory? How does it differ from valence bond theory?

Sketch the shapes of the following molecular orbitals: 1s, w 1s, 2p, and w 2p. How do their energies compare?

Compare the Lewis theory, valence bond theory, and molecular orbital theory of chemical bonding.

Explain the significance of bond order. Can bond order be used for quantitative comparisons of the strengths of chemical bonds?

Explain in molecular orbital terms the changes in HH internuclear distance that occur as the molecular H2 is ionized first to H2 1 and then to H2 21

The formation of H2 from two H atoms is an energetically favorable process. Yet statistically there is less than a 100 percent chance that any two H atoms will undergo the reaction. Apart from energy considerations, how would you account for this observation based on the electron spins in the two H atoms?

Draw a molecular orbital energy level diagram for each of the following species: He2, HHe, He2 1. Compare their relative stabilities in terms of bond orders. (Treat HHe as a diatomic molecule with three electrons.)

Arrange the following species in order of increasing stability: Li2, Li2 1, Li2 2. Justify your choice with a molecular orbital energy level diagram

Use molecular orbital theory to explain why the Be2 molecule does not exist.

Which of these species has a longer bond, B2 or B2 1? Explain in terms of molecular orbital theory.

Acetylene (C2H2) has a tendency to lose two protons (H1) and form the carbide ion (C2 22), which is present in a number of ionic compounds, such as CaC2 and MgC2. Describe the bonding scheme in the C2 22 ion in terms of molecular orbital theory. Compare the bond order in C2 22 with that in C2.

Compare the Lewis and molecular orbital treatments of the oxygen molecule.

Explain why the bond order of N2 is greater than that of N2 1, but the bond order of O2 is less than that of O2 1.

Compare the relative stability of the following species and indicate their magnetic properties (that is, diamagnetic or paramagnetic): O2, O2 1, O2 2 (superoxide ion), O2 22 (peroxide ion).

Use molecular orbital theory to compare the relative stabilities of F2 and F2 1.

A single bond is almost always a sigma bond, and a double bond is almost always made up of a sigma bond and a pi bond. There are very few exceptions to this rule. Show that the B2 and C2 molecules are examples of the exceptions.

In 2009 the ion N2 32 was isolated. Use a molecular orbital diagram to compare its properties (bond order and magnetism) with the isoelectronic ion O2 2.

The following potential energy curve represents the formation of F2 from two F atoms. Describe the state of bonding at the marked regions. Potential energy r 0 + 3 4 5 2 1

How does a delocalized molecular orbital differ from a molecular orbital such as that found in H2 or C2H4? What do you think are the minimum conditions (for example, number of atoms and types of orbitals) for forming a delocalized molecular orbital?

In Chapter 9 we saw that the resonance concept is useful for dealing with species such as the benzene molecule and the carbonate ion. How does molecular orbital theory deal with these species?

Both ethylene (C2H4) and benzene (C6H6) contain the CC bond. The reactivity of ethylene is greater than that of benzene. For example, ethylene readily reacts with molecular bromine, whereas benzene is normally quite inert toward molecular bromine and many other compounds. Explain this difference in reactivity

Explain why the symbol on the left is a better representation of benzene molecules than that on the right

Determine which of these molecules has a more delocalized orbital and justify your choice. (Hint: Both molecules contain two benzene rings. In naphthalene, the two rings are fused together. In biphenyl, the two rings are joined by a single bond, around which the two rings can rotate.)

Nitryl fluoride (FNO2) is very reactive chemically. The fluorine and oxygen atoms are bonded to the nitrogen atom. (a) Write a Lewis structure for FNO2. (b) Indicate the hybridization of the nitrogen atom. (c) Describe the bonding in terms of molecular orbital theory. Where would you expect delocalized molecular orbitals to form?

Describe the bonding in the nitrate ion NO3 2 in terms of delocalized molecular orbitals.

What is the state of hybridization of the central O atom in O3? Describe the bonding in O3 in terms of delocalized molecular orbitals.

Which of the following species is not likely to have a tetrahedral shape? (a) SiBr4, (b) NF4 1, (c) SF4, (d) BeCl4 22, (e) BF4 2, (f) AlCl4 2

Draw the Lewis structure of mercury(II) bromide. Is this molecule linear or bent? How would you establish its geometry?

Sketch the bond moments and resultant dipole moments for the following molecules: H2O, PCl3, XeF4, PCl5, SF6.

Although both carbon and silicon are in Group 4A, very few SiSi bonds are known. Account for the instability of silicon-to-silicon double bonds in general. (Hint: Compare the atomic radii of C and Si in Figure 8.5. What effect would the larger size have on pi bond formation?)

Acetaminophen is the active ingredient in Tylenol. (a) Write the molecular formula of the compound. (b) What is the hybridization state of each C, N, and O atom? (c) Describe the geometry about each C, N, and O atom.

Caffeine is a stimulant drug present in coffee. (a) Write the molecular formula of the compound. (b) What is the hybridization state of each C, N, and O atom? (c) Describe the geometry about each C, N, and O atom.

7 Predict the geometry of sulfur dichloride (SCl2) and the hybridization of the sulfur atom.

Antimony pentafluoride, SbF5, reacts with XeF4 and XeF6 to form ionic compounds, XeF3 1SbF6 2 and XeF5 1SbF6 2. Describe the geometries of the cations and anion in these two compounds.

Draw Lewis structures and give the other information requested for the following molecules: (a) BF3. Shape: planar or nonplanar? (b) ClO3 2. Shape: planar or nonplanar? (c) H2O. Show the direction of the resultant dipole moment. (d) OF2. Polar or nonpolar molecule? (e) NO2. Estimate the ONO bond angle.

Draw Lewis structures and give the other information requested for the following molecules: (a) BF3. Shape: planar or nonplanar? (b) ClO3 2. Shape: planar or nonplanar? (c) H2O. Show the direction of the resultant dipole moment. (d) OF2. Polar or nonpolar molecule? (e) NO2. Estimate the ONO bond angle.

Briefly compare the VSEPR and hybridization approaches to the study of molecular geometry.

Describe the hybridization state of arsenic in arsenic pentafluoride (AsF5).

Draw Lewis structures and give the other information requested for the following: (a) SO3. Polar or nonpolar molecule? (b) PF3. Polar or nonpolar molecule? (c) F3SiH. Show the direction of the resultant dipole moment. (d) SiH3 2. Planar or pyramidal shape? (e) Br2CH2. Polar or nonpolar molecule?

Which of the following molecules and ions are linear? ICl2 2, IF2 1, OF2, SnI2, CdBr2

Draw the Lewis structure for the BeCl4 22 ion. Predict its geometry and describe the hybridization state of the Be atom.

The N2F2 molecule can exist in either of the following two forms: G D F F D DF F NPN NPN (a) What is the hybridization of N in the molecule? (b) Which structure has a dipole moment?

Cyclopropane (C3H6) has the shape of a triangle in which a C atom is bonded to two H atoms and two other C atoms at each corner. Cubane (C8H8) has the shape of a cube in which a C atom is bonded to one H atom and three other C atoms at each corner. (a) Draw Lewis structures of these molecules. (b) Compare the CCC angles in these molecules with those predicted for an sp3 -hybridized C atom. (c) Would you expect these molecules to be easy to make?

The compound 1,2-dichloroethane (C2H4Cl2) is nonpolar, while cis-dichloroethylene (C2H2Cl2) has a dipole moment: Cl A A H Cl A A H 1,2-dichloroethane cis-dichloroethylene CPC ClG H D DCl G H HOCOCOH The reason for the difference is that groups connected by a single bond can rotate with respect to each other, but no rotation occurs when a double bond connects the groups. On the basis of bonding considerations, explain why rotation occurs in 1,2-dichloroethane but not in cis- dichloroethylene

Does the following molecule have a dipole moment? CPCPC ClG H D D H G Cl (Hint: See the answer to Problem 10.39.)

So-called greenhouse gases, which contribute to global warming, have a dipole moment or can be bent or distorted into shapes that have a dipole moment. Which of the following gases are greenhouse gases? N2, O2, O3, CO, CO2, NO2, N2O, CH4, CFCl3

The bond angle of SO2 is very close to 1208, even though there is a lone pair on S. Explain

39-azido-39-deoxythymidine, shown here, commonly known as AZT, is one of the drugs used to treat acquired immune deficiency syndrome (AIDS). What are the hybridization states of the C and N atoms in this molecule? A C A H O O B A A A C A H HOOCH2 H A C A N B N B N H A C A H NECHC A B CHNEC OK HH OCH3 HH

The following molecules (AX4Y2) all have octahedral geometry. Group the molecules that are equivalent to each other. X X Y Y A X X Y X X Y A X X X X Y X A X Y X X Y X A Y X (a) (b) (c) (d)

The compounds carbon tetrachloride (CCl4) and silicon tetrachloride (SiCl4) are similar in geometry and hybridization. However, CCl4 does not react with water but SiCl4 does. Explain the difference in their chemical reactivities. (Hint: The first step of the reaction is believed to be the addition of a water molecule to the Si atom in SiCl4.)

Write the ground-state electron configuration for B2. Is the molecule diamagnetic or paramagnetic?

What are the hybridization states of the C and N atoms in this molecule? A NH2 A H NKCHC A B CHNEC OK HH EH

Use molecular orbital theory to explain the difference between the bond enthalpies of F2 and F2 2 (see Problem 9.110).

Referring to the Chemistry in Action essay on p. 426, answer the following questions: (a) If you wanted to cook a roast (beef or lamb), would you use a microwave oven or a conventional oven? (b) Radar is a means of locating an object by measuring the time for the echo of a microwave from the object to return to the source and the direction from which it returns. Would radar work if oxygen, nitrogen, and carbon dioxide were polar molecules? (c) In early tests of radar at the English Channel during World War II, the results were inconclusive even though there was no equipment malfunction. Why? (Hint: The weather is often foggy in the region.)

Which of the following molecules are polar? (a) (b) (c)

Which of the following molecules are polar? (a) (b) (c)

The stable allotropic form of phosphorus is P4, in which each P atom is bonded to three other P atoms. Draw a Lewis structure of this molecule and describe its geometry. At high temperatures, P4 dissociates to form P2 molecules containing a PP bond. Explain why P4 is more stable than P2.

Referring to Table 9.4, explain why the bond enthalpy for Cl2 is greater than that for F2. (Hint: The bond lengths of F2 and Cl2 are 142 pm and 199 pm, respectively.)

Use molecular orbital theory to explain the bonding in the azide ion (N3 2). (Arrangement of atoms is NNN.)

The ionic character of the bond in a diatomic molecule can be estimated by the formula ed 3 100% where is the experimentally measured dipole moment (in C m), e the electronic charge, and d the bond length in meters. (The quantity ed is the hypothetical dipole moment for the case in which the transfer of an electron from the less electronegative to the more electronegative atom is complete.) Given that the dipole moment and bond length of HF are 1.92 D and 91.7 pm, respectively, calculate the percent ionic character of the molecule.

Draw three Lewis structures for compounds with the formula C2H2F2. Indicate which of the compound(s) are polar.

Greenhouse gases absorb (and trap) outgoing infrared radiation (heat) from Earth and contribute to global warming. The molecule of a greenhouse gas either possesses a permanent dipole moment or has a changing dipole moment during its vibrational motions. Consider three of the vibrational modes of carbon dioxide OPCPO OPCPO OPCPO g m n n nm h h where the arrows indicate the movement of the atoms. (During a complete cycle of vibration, the atoms move toward one extreme position and then reverse their direction to the other extreme position.) Which of the preceding vibrations are responsible for CO2 to behave as a greenhouse gas? Which of the following molecules can act as a greenhouse gas: N2, O2, CO, NO2, and N2O?

Aluminum trichloride (AlCl3) is an electron- deficient molecule. It has a tendency to form a dimer (a molecule made of two AlCl3 units): AlCl3 1 AlCl3 S Al2Cl6 (a) Draw a Lewis structure for the dimer. (b) Describe the hybridization state of Al in AlCl3 and Al2Cl6. (c) Sketch the geometry of the dimer. (d) Do these molecules possess a dipole moment?

The molecules cis-dichloroethylene and transdichloroethylene shown on p. 425 can be interconverted by heating or irradiation. (a) Starting with cisdichloroethylene, show that rotating the CC bond by 180 will break only the pi bond but will leave the sigma bond intact. Explain the formation of trans- dichloroethylene from this process. (Treat the rotation as two stepwise 90 rotations.) (b) Account for the difference in the bond enthalpies for the pi bond (about 270 kJ/mol) and the sigma bond (about 350 kJ/mol). (c) Calculate the longest wavelength of light needed to bring about this conversion.

Progesterone is a hormone responsible for female sex characteristics. In the usual shorthand structure, each point where lines meet represent a C atom, and most H atoms are not shown. Draw the complete structure of the molecule, showing all C and H atoms. Indicate which C atoms are sp2 - and sp3 -hybridized. O CH3 C K A A CH3A A CH3 PO

For each pair listed here, state which one has a higher first ionization energy and explain your choice: (a) H or H2, (b) N or N2, (c) O or O2, (d) F or F2.

The molecule benzyne (C6H4) is a very reactive species. It resembles benzene in that it has a sixmembered ring of carbon atoms. Draw a Lewis structure of the molecule and account for the molecules high reactivity

Assume that the third-period element phosphorus forms a diatomic molecule, P2, in an analogous way as nitrogen does to form N2. (a) Write the electronic configuration for P2. Use [Ne2] to represent the electron configuration for the first two periods. (b) Calculate its bond order. (c) What are its magnetic properties (diamagnetic or paramagnetic)?

Consider a N2 molecule in its first excited electronic state; that is, when an electron in the highest occupied molecular orbital is promoted to the lowest empty molecular orbital. (a) Identify the molecular orbitals involved and sketch a diagram to show the transition. (b) Compare the bond order and bond length of N2* with N2, where the asterisk denotes the excited molecule. (c) Is N2* diamagnetic or paramagnetic? (d) When N2* loses its excess energy and converts to the ground state N2, it emits a photon of wavelength 470 nm, which makes up part of the auroras lights. Calculate the energy difference between these levels.

As mentioned in the chapter, the Lewis structure for O2 is OQ O O O PQ Use the molecular orbital theory to show that the structure actually corresponds to an excited state of the oxygen molecule. 10.115 Referring to Problem 9.137, describe the hybridization state of the N atoms and the overall shape of the ion

Describe the geometry and hybridization for the reactants and product in the following reaction ClF3 1 AsF5 [ClF1 2 ][AsF2 6 ]

Describe the geometry and hybridization for the reactants and product in the following reaction ClF3 1 AsF5 [ClF1 2 ][AsF2 6 ]

Draw the Lewis structure of ketene (C2H2O) and describe the hybridization states of the C atoms. The molecule does not contain OH bonds. On separate diagrams, sketch the formation of sigma and pi bonds.

TCDD, or 2,3,7,8-tetrachlorodibenzo-p-dioxin, is a highly toxic compound EO Cl O Cl Cl ECl E E E E E E It gained considerable notoriety in 2004 when it was implicated in the murder plot of a Ukrainian politician. (a) Describe its geometry and state whether the molecule has a dipole moment. (b) How many pi bonds and sigma bonds are there in the molecule?

Write the electron configuration of the cyanide ion (CN2). Name a stable molecule that is isoelectronic with the ion.

Carbon monoxide (CO) is a poisonous compound due to its ability to bind strongly to Fe21 in the hemoglobin molecule. The molecular orbitals of CO have the same energy order as those of the N2 molecule. (a) Draw a Lewis structure of CO and assign formal charges. Explain why CO has a rather small dipole moment of 0.12 D. (b) Compare the bond order of CO with that from molecular orbital theory. (c) Which of the atoms (C or O) is more likely to form bonds with the Fe21 ion in hemoglobin?

The geometries discussed in this chapter all lend themselves to fairly straightforward elucidation of bond angles. The exception is the tetrahedron, because its bond angles are hard to visualize. Consider the CCl4 molecule, which has a tetrahedral geometry and is nonpolar. By equating the bond moment of a particular CCl bond to the resultant bond moments of the other three CCl bonds in opposite directions, show that the bond angles are all equal to 109.5

Carbon suboxide (C3O2) is a colorless pungentsmelling gas. Does it possess a dipole moment?

Which of the following ions possess a dipole moment? (a) ClF2 1, (b) ClF2 2, (c) IF4 1, (d) IF4 2.

Given that the order of molecular orbitals for NO is similar to that for O2, arrange the following species in increasing bond orders: NO22, NO2, NO, NO1, NO21.

Shown here are molecular models of SX4 for X 5 F, Cl, and Br. Comment on the trends in the bond angle between the axial SX bonds in these molecules. SF4 SCl4 SBr4

Based on what you have learned from this chapter and Chapter 9, name a diatomic molecule that has the strongest known chemical bond and one with the weakest known chemical bond

The stability of benzene is due to the fact that we can draw reasonable resonance structures for the molecule, which is equivalent to saying that there is electron delocalization. Resonance energy is a measure of how much more stable benzene is compared to the hypothetical molecule, which can be represented by just a single resonance structure. Shown on p. 464 are the enthalpies of hydrogenation (the addition of hydrogen) of cyclohexene (C6H10) to cyclohexane (C6H12) and benzene to cyclohexane.1 H2 DH8 5 2120 kJ/mol1 3H2 DH8 5 2208 kJ/mol(In these simplified structures, each point wherelines meet represents a C atom. There is a H atomattached ta sp2- hybridized C atom and there aretwo H atoms attached to a sp3-hybridized C atom.)Estimate the resonance energy of benzene fromthese data.

How many carbon atoms are contained in one square centimeter of graphene (see the Chemistry in Action essay on p. 454 for a description of graphene)? What would be the mass of a 1-cm2 section of graphene?

Problem 1E Why is molecular geometry important? Cite some examples.

Problem 1SAQ Determine the molecular geometry of CBr4 . a) linear b) trigonal planar c) tetrahedral d) trigonal pyramidal

Problem 2E According to VSEPR theory, what determines the geometry of a molecule?

Problem 2SAQ Determine the molecular geometry of SeF4 . a) tetrahedral b) trigonal bipyramidal c) T-shaped d) seesaw

Problem 3E Name and sketch the five basic electron geometries, and state the number of electron groups corresponding to each. What constitutes an electron group ?

Problem 3SAQ Predict the relative bond angles in BF3 and S02 . a) BF3 bond angles > S02 bond angle b) S02 bond angle > BF3 bond angles c) BF3 bond angles = S02 bond angle d) Relative bond angles cannot be predicted.

Explain the difference between electron geometry and molecular geometry. Under what circumstances are they not the same?

Predict the molecular geometry about N in the molecule CH3NHCH3. a) linear b) trigonal planar c) trigonal pyramidal d) bent

Problem 5E Give the correct electron and molecular geometries that correspond to each set of electron groups around the central atom of a molecule. a. four electron groups overall; three bonding groups and one lone pair b. four electron groups overall; two bonding groups and two lone pairs c. five electron groups overall; four bonding groups and one lone pair d. five electron groups overall; three bonding groups and two lone pairs e. five electron groups overall; two bonding groups and three lone pairs f. six electron groups overall; five bonding groups and one lone pair g. six electron groups overall; four bonding groups and two lone pairs

Which molecule is polar? a) \(SF_2\) b) \(BH_3\) c) \(PF_5\) d) \(CS_2\)

Problem 6E How do you apply VSEPR theory to predict the shape of a molecule with more than one interior atom?

Determine the hybridization about O in CH 3 OH. a) sp b) sp2 c) sp3 d) sp3d

Problem 7E How do you determine if a molecule is polar? Why is polarity important?

Determine the hybridization about C in H2CO. a) sp b) sp2 c) sp3 d) sp3d

Problem 8E What is a chemical bond according to valence bond theory?

According to valence bond theory, which kind of orbitals overlap to form the P—Cl bonds in PCl5? a) P(sp3) - Cl(p) b) P(sp3d) - Cl(s) c) P(sp3) - Cl(s) d) P(sp3d) - Cl(p)

Problem 9E In valence bond theory, what determines the geometry of a molecule?

Use molecular orbital theory to determine the bond order in C2. a) 0 b) 1 c) 2 d) 3

In valence bond theory, the interaction energy between the electrons and nucleus of one atom with the electrons and nucleus of another atom is usually negative (stabilizing) when ________.

Use molecular orbital theory to predict which species has the strongest bond. a) N2 b) N2- c) N2+ d) All bonds are equivalent according to molecular orbital theory.

Problem 11E What is hybridization? Why is hybridization necessary in valence bond theory?

Use molecular orbital theory to determine which molecule is diamagnetic. a. CO b. \(\mathrm{B}_{2}\) c. \(\mathrm{O}_{2}\) d. None of the above (all are paramagnetic)

Problem 12E How does hybridization of the atomic orbitals in the central atom of a molecule help lower the overall energy of the molecule?

Which hybridization scheme occurs about nitrogen when nitrogen forms a double bond? a) sp b) sp2 c) sp3 d) sp3d

Problem 13SAQ Which molecule geometry results when a central atom has five total electron groups, with three of those being bonding groups and two being lone pairs? a) trigonal bipyramidal b) seesaw c) T-shaped d) bent

Determine the correct molecular geometry (from left to right) about each interior atom in CH3CH2OH. a) 1st C tetrahedral; 2nd C trigonal planar; O linear b) 1st C trigonal planar; 2nd C bent; O linear c) 1st C trigonal planar; 2nd C trigonal pyramidal; O bent d) 1st C tetrahedral; 2nd C tetrahedral; O bent

The central atom in a molecule has a bent molecular geometry. Determine the hybridization of the orbitals in the atom. a) sp b) sp2 c) sp3 d) Hybridization cannot be determine from information given.

Problem 28E When applying molecular orbital theory to heteronuclear diatomic molecules, the atomic orbitals used may be of different energies. If two atomic orbitals of different energies make two molecular orbitals, how are the energies of the molecular orbitals related to the energies of the atomic orbitals? How is the shape of the resultant molecular orbitals related to the shapes of the atomic orbitals?

Determine whether each molecule is polar or nonpolar. a. SiCl4 b. CF2Cl2 c. SeF6 d. IF5

Which hybridization scheme allows the central atom to form more than four bonds?

Write a hybridization and bonding scheme for each molecule. Sketch the molecule, including overlapping orbitals, and label all bonds using the notation shown in Examples 10.6 and 10.7. a. \(CCl_4\) b. \(NH_3\) c. \(OF_2\) d. \(CO_2\)

Write a hybridization and bonding scheme for each molecule or ion. Sketch the structure, including overlapping orbitals, and label all bonds using the notation shown in Examples 10.6 and 10.7. a. COCl2 (carbon is the central atom) b. BrF5 c. XeF2 d. I3-.

Write a hybridization and bonding scheme for each molecule. Sketch the molecule, including overlapping orbitals, and label all bonds using the notation shown in Examples 10.6 and 10.7. a. \(\mathrm{CH}_{2} \mathrm{Br}_{2}\) b. \(\mathrm{SO}_{2}\) c. \(\mathrm{NF}_{3}\) d. \(\mathrm{BF}_{3}\)

Write a hybridization and bonding scheme for each molecule or ion. Sketch the structure, including overlapping orbitals, and label all bonds using the notation shown in Examples 10.6 and 10.7. a. SO32- b. PF6- c. BrF3 d. HCN

Write a hybridization and bonding scheme for each molecule that contains more than one interior atom. Indicate the hybridization about each interior atom. Sketch the structure, including overlapping orbitals, and label all bonds using the notation shown in Examples 10.6 and 10.7. a. N2H2 (skeletal structure HNNH) b. N2H4 (skeletal structure H2NNH2 ) c. CH3NH2 (skeletal structure H3CNH2 )

Write a hybridization and bonding scheme for each molecule that contains more than one interior atom. Indicate the hybridization about each interior atom. Sketch the structure, including overlapping orbitals, and label all bonds using the notation shown in Examples 10.6 and 10.7. a. C2H2 (skeletal structure HCCH) b. C2H4 (skeletal structure H2CCH2 ) c. C2H6 (skeletal structure H3CCH3 )

Consider the structure of the amino acid alanine. Indicate the hybridization about each interior atom.

Consider the structure of the amino acid aspartic acid. Indicate the hybridization about each interior atom.

Problem 69E Sketch the bonding molecular orbital that results from the linear combination of two 1 s orbitals. Indicate the region where interference occurs and state the kind of interference (constructive or destructive).

Problem 70E Sketch the antibonding molecular orbital that results from the linear combination of two 1 s orbitals. Indicate the region where interference occurs and state the kind of interference (constructive or destructive).

Draw an MO energy diagram and predict the bond order of Be2+ and Be2-. Do you expect these molecules to exist in the gas phase?

Draw an MO energy diagram and predict the bond order of Li2+ and Li2-. Do you expect these molecules to exist in the gas phase?

Sketch the bonding and antibonding molecular orbitals that result from linear combinations of the 2px atomic orbitals in a homonuclear diatomic molecule. (The 2px orbitals are those whose lobes are oriented along the bonding axis.)

Sketch the bonding and antibonding molecular orbitals that result from linear combinations of the \(2 p_{z}\) atomic orbitals in a homonuclear diatomic molecule. (The \(2 p_{z}\) orbitals are those whose lobes are oriented perpendicular to the bonding axis.) How do these molecular orbitals differ from those obtained from linear combinations of the \(2 p_{y}\) atomic orbitals? (The \(2 p_{y}\) orbitals are also oriented perpendicular to the bonding axis, but also perpendicular to the \(2 p_{z}\) orbitals.)

Using the molecular orbital energy ordering for second-row homonuclear diatomic molecules in which the 2p orbitals lie at lower energy than the 2p, draw MO energy diagrams and predict the bond order in a molecule or ion with each number of total valence electrons. Will the molecule or ion be diamagnetic or paramagnetic? a. 4 b. 6 c. 8 d. 9

Using the molecular orbital energy ordering for second-row homonuclear diatomic molecules in which the \(\pi_{2 p}\) orbitals lie at higher energy than the \(\sigma_{2 p}\), draw MO energy diagrams and predict the bond order in a molecule or ion with each number of total valence electrons. Will the molecule or ion be diamagnetic or paramagnetic? (a) 10 (b) 12 (c) 13 (d) 14

Use molecular orbital theory to predict if each molecule or ion exists in a relatively stable form. a. \(\mathrm{H}_{2}{ }^{2-}\) b. \(\mathrm{Ne}_{2}\) c. \(\mathrm{He}_{2}^{2+}\) d. \(\mathrm{F}_{2}^{2-}\)

Use molecular orbital theory to predict if each molecule or ion exists in a relatively stable form. a. C22+ b. Li2 c. Be22+ d. Li22+

According to MO theory, which molecule or ion has the highest bond order? Highest bond energy? Shortest bond length?

According to MO theory, which molecule or ion has the highest bond order? Highest bond energy? Shortest bond length?

Draw an MO energy diagram for CO. (Use the energy ordering of O2. ) Predict the bond order and make a sketch of the lowest energy bonding molecular orbital.

Problem 82E Draw an energy diagram for HCI. Predict the bond order and make a sketch of the lowest energy bonding molecular orbital.

For each compound, draw the Lewis structure, determine the geometry using VSEPR theory, determine whether the molecule is polar, identify the hybridization of all interior atoms, and make a sketch of the molecule, according to valence bond theory, showing orbital overlap. a. COF2 (carbon is the central atom) b. S2Cl2 (ClSSCl) c. SF4

For each compound, draw the Lewis structure, determine the geometry using VSEPR theory, determine whether the molecule is polar, identify the hybridization of all interior atoms, and make a sketch of the molecule, according to valence bond theory, showing orbital overlap. a. IF5 b. CH2CHCH3 c. CH3SH

Amino acids are biological compounds that link together to form proteins, the workhorse molecules in living organisms. The skeletal structures of several simple amino acids are shown here. For each skeletal structure, complete the Lewis structure, determine the geometry and hybridization about each interior atom, and make a sketch of the molecule, using the bond conventions of Section 10.4.

The genetic code is based on four different bases with the structures shown here. Assign a geometry and hybridization to each interior atom in these four bases. a. cytosine b. adenine c. thymine d. Guanine

The structure of caffeine, present in coffee and many soft drinks, is shown here. How many pi bonds are present in caffeine? How many sigma bonds? Insert the lone pairs in the molecule. What kinds of orbitals do the lone pairs occupy?

The structure of acetylsalicylic acid (aspirin) is shown here. How many pi bonds are present in acetylsalicylic acid? How many sigma bonds? What parts of the molecule are free to rotate? What parts are rigid?

Most vitamins can be classified either as fat soluble, which results in their tendency to accumulate in the body (so that taking too much can be harmful), or water soluble, which results in their tendency to be quickly eliminated from the body in urine. Examine the structural formulas and space-filling models of these vitamins and determine whether each one is fat soluble (mostly nonpolar) or water soluble (mostly polar).

Water does not easily remove grease from dishes or hands, because grease is nonpolar and water is polar. The addition of soap to water, however, allows the grease to dissolve. Study the structure of sodium stearate (a soap) and describe how it works.

Draw a molecular orbital energy diagram for ClF. (Assume that the p orbitals are lower in energy than the orbitals.) What is the bond order in ClF?

Draw Lewis structures and MO diagrams for CN+, CN, and CN-. According to the Lewis model, which species is most stable? According to MO theory, which species is most stable? Do the two theories agree?

Problem 93E Bromine can form compounds or ions with any number of fluorine atoms from one to five. Write the formulas of all five of these species, assign a hybridization, and describe their electron and molecular geometry.

The compound \(\mathrm{C}_3 \mathrm{H}_4\) has two double bonds. Describe its bonding and geometry, using a valence bond approach.

Draw the structure of a molecule with the formula C4H6CI2 that has a dipole moment of 0.

Draw the structures of two compounds that have the composition CH3NO2 and have all three H atoms bonded to the C. Predict which compound has the larger ONO bond angle.

How many hybrid orbitals do we use to describe each molecule? a. \(\mathrm{N}_{2} \mathrm{O}_{5}\) b. \(\mathrm{C}_{2} \mathrm{H}_{5} \mathrm{NO}\) (four \(\mathrm{C}-\mathrm{H}\) bonds and one \(\mathrm{O}-\mathrm{H}\) bond) c. BrCN (no formal charges)

Indicate which orbitals overlap to form the s bonds in the following. a. BeBr2 b. HgCl2 c. ICN

In VSEPR theory, which uses the Lewis model to determine molecular geometry, the trend of decreasing bond angle in CH4, NH3, and H2O is accounted for by the greater repulsion of lone pair electrons compared to bonding pair electrons. How would this trend be accounted for in valence bond theory?

The results of a molecular orbital calculation for H2O are shown here. Examine each of the orbitals and classify them as bonding, antibonding, or nonbonding. Assign the correct number of electrons to the energy diagram. According to this energy diagram, is H2O stable? Explain.

The results of a molecular orbital calculation for NH3 are shown here. Examine each of the orbitals and classify them as bonding, antibonding, or nonbonding. Assign the correct number of electrons to the energy diagram. According to this energy diagram, is NH3 stable? Explain.

cis-2-Butene isomerizes to trans-2-butene via the reaction a. If isomerization requires breaking the \(\pi\) bond, what minimum energy is required for isomerization in J/mol? In J/molecule? b. If the energy for isomerization came from light, what minimum frequency of light would be required? In what portion of the electromagnetic spectrum does this frequency lie?

The species NO2, NO2+, and NO2- in which N is the central atom, have very different bond angles. Predict what these bond angles might be with respect to the ideal angles and justify your prediction.

The bond angles increase steadily in the series PF3, PCl3, PBr3, and PI3. After consulting the data on atomic radii in Chapter 8 , provide an explanation for this observation.

The ion CH5+ can form under very special high-energy conditions in the vapor phase in a mass spectrometer. Propose a hybridization for the carbon atom and predict the geometry.

Neither the VSEPR model nor the hybridization model is able to account for the experimental observation that the F __ Ba __ F bond angle in gaseous BaF2 is 108o rather than the predicted 180o. Suggest some possible explanations for this observation.

Draw the Lewis structure for acetamide (CH3CONH2), an organic compound, and determine the geometry about each interior atom. Experiments show that the geometry about the nitrogen atom in acetamide is nearly planar. What resonance structure can account for the planar geometry about the nitrogen atom?

Use VSEPR to predict the geometry (including bond angles) about each interior atom of methyl azide (CH3N3), and make a sketch of the molecule. Would you expect the bond angle between the two interior nitrogen atoms to be the same or different? Would you expect the two nitrogen–nitrogen bond lengths to be the same or different?

Problem 109E Which statement best captures the fundamental idea behind VSEPR theory? Explain what is wrong with each of the other statements. a. The angle between two or more bonds is determined primarily by the repulsions between the electrons within those bonds and other (lone pair) electrons on the central atom of a molecule. Each of these electron groups (bonding electrons or lone pair electrons) will lower its potential energy by maximizing its separation from other electron groups, thus determining the geometry of the molecule. b. The angle between two or more bonds is determined primarily by the repulsions between the electrons within those bonds. Each of these bonding electrons will lower its potential energy by maximizing its separation from other electron groups, thus determining the geometry of the molecule. c. The geometry of a molecule is determined by the shapes of the overlapping orbitals that form the chemical bonds. Therefore, to determine the geometry of a molecule, you must determine the shapes of the orbitals involved in bonding.

Problem 110E Suppose that a molecule has four bonding groups and one lone pair on the central atom. Suppose further that the molecule is confined to two dimensions (this is a purely hypothetical assumption for the sake of understanding the principles behind VSEPR theory). Make a sketch of the molecule and estimate the bond angles.

Problem 111E How does each of the three major bonding theories (the Lewis model, valence bond theory, and molecular orbital theory) define a single chemical bond? A double bond? A triple bond? How are these definitions similar? How are they different?

Problem 112E The most stable forms of the nonmetals in groups 4A, 5A,and 6A of the first period are molecules with multiple bonds. Beginning with the second period, the most stable forms of the nonmetals of these groups are molecules without multiple bonds. Propose an explanation for this observation based on valence bond theory.

How is Amy Tans use of the phrase mother tongue ambiguous?

What does Tan mean by the power of language (para. 2)? What does that phrase mean to you?

What are the different En glishes (para. 3) Tan describes in this essay? How does each have its own type of power?

How would you describe Tans attitude toward her mother?

What does Tan mean when she says, I think my mothers En glish almost had an effect on limiting my possibilities in life as well (para. 15)? To what extent do you

What is the associative situation (para. 17) that Tan claims accounts for her high performance on math tests but not on En glish tests specifically, analogies?

Why does Tan believe that envisioning a reader specifically, her mother enabled her to write more authentically?

What are some of the class and cultural distinctions that people encounter because of their inability to use standardized En glish, according to Tan?

This essay was first published in Threepenny Review, which the novelist Jonathan Franzen has described as one of the few magazines left in this country which seem pitched at the general literary reader and which consistently publish such interesting, high- quality criticism, reflection, argument, fiction, and poetry. How does Tan appeal to this audience of general literary reader[s]?

Find examples in the essay where Orwell is guilty of the four faults that characterize the writing he is criticizing

Apply the following definition of slang from Whitmans essay to examples that you know from your own experience or study: an attempt of common humanity to escape from bald literalism, and express itself illimitably, which in highest walks produces poets and poems . . . (para. 2).

A more current essay by Tom Dalzell, an expert on American slang, examines the impact of young people on its development: Whatever its source, youth slang is a core element of youth culture, as a defiant gesture of resistance and an emblem of tribe identity. Fashion and hair styles are other key manifestations of a generations identity, but they can be easily regulated by adult authorities. With music and language, regulation and restriction are much more difficult. Even the most vigilant and repressive attempts by adult authority cannot completely eradicate slang and music with its slang lyrics. Support, challenge, or qualify this view with evidence from your own generation or another with which you are familiar.

What similarities do you see among the sources that Anzalda has cited? What is the purpose of notes 11 and 13? Do you think it would have been more effective if Anzalda had incorporated these points within the text of her argument? Explain why or why not.

This essay was published in 1987, long before the day we now know as 9/11. Do you think that the new historical reality argues for changing the section heading entitled Linguistic Terrorism, or does this reality make the heading even more powerful? Explain your viewpoint.

Maya has a lot of sympathy for students who experience test anxiety

In Politics and the En glish Language, George Orwell cites the following paragraph as an example of bad writing. Revise the paragraph by eliminating pretentious diction and improving clarity. On the one side we have the free personality: by definition it is not neurotic, for it has neither conflict nor dream. Its desires, such as they are, are transparent, for they are just what institutional approval keeps in the forefront of consciousness; another institutional pattern would alter their number and intensity; there is little in them that is natural, irreducible, or culturally dangerous. But on the other side, the social bond itself is nothing but the mutual reflection of these self- secure integrities. Recall the definition of love. Is not this the very picture of a small aca demic? Where is there a place in this hall of mirrors for either personality or fraternity?

Find an article in a newspaper, a memo from an organization, or a speech that contains examples of pretentious and awkward diction. Identify the examples, and explain their effect. Suggest ways to revise that would make the writing clearer. Do you think the writer is intentionally keeping the language obscure? If so, why might that be the case?

Name the hybridization scheme that corresponds to each electron geometry: a. linear b. trigonal planar c. tetrahedral d. trigonal bipyramidal e. octahedral

What is a chemical bond according to molecular orbital theory?

Explain the difference between hybrid atomic orbitals in valence bond theory and LCAO molecular orbitals in molecular orbital theory.

What is a bonding molecular orbital?

What is an antibonding molecular orbital?

What is the role of wave interference in determining whether a molecular orbital is bonding or antibonding?

In molecular orbital theory, what is bond order? Why is it important?

How is the number of molecular orbitals approximated by a linear combination of atomic orbitals related to the number of atomic orbitals used in the approximation?

Sketch each molecular orbital. a. \(\sigma_{2 s}\) b. \(\sigma_{2 s}^{*}\) c. \(\sigma_{2 p}\) d. \(\sigma_{2 p}^{*}\) e. \(\pi_{2 p}\) f. \(\pi_{2 p}^{*}\)

Draw an energy diagram for the molecular orbitals of period 2 diatomic molecules. Show the difference in ordering for B2, C2, and N2 compared to O2, F2, and Ne2.

Why does the energy ordering of the molecular orbitals of the period 2 diatomic molecules change in going from N2 to O2?

Explain the difference between a paramagnetic species and a diamagnetic one.

When applying molecular orbital theory to heteronuclear diatomic molecules, the atomic orbitals used may be of different energies. If two atomic orbitals of different energies make two molecular orbitals, how are the energies of the molecular orbitals related to the energies of the atomic orbitals? How is the shape of the resultant molecular orbitals related to the shapes of the atomic orbitals?

In molecular orbital theory, what is a nonbonding orbital?

Write a short paragraph describing chemical bonding according to the Lewis model, valence bond theory, and molecular orbital theory. Indicate how the theories differ in their description of a chemical bond and indicate the strengths and weaknesses of each theory. Which theory is correct?

A molecule with the formula AB3 has a trigonal pyramidal geometry. How many electron groups are on the central atom (A)?

A molecule with the formula \(\mathrm{AB}_{3}\) has a trigonal planar geometry. How many electron groups are on the central atom?

For each molecular geometry, list the number of total electron groups, the number of bonding groups, and the number of lone pairs on the central atom.

For each molecular geometry, list the number of total electron groups, the number of bonding groups, and the number of lone pairs on the central atom.

Determine the electron geometry, molecular geometry, and idealized bond angles for each molecule. In which cases do you expect deviations from the idealized bond angle? a. PF3 b. SBr2 c. CHCl3 d. CS2

Determine the electron geometry, molecular geometry, and idealized bond angles for each molecule. In which cases do you expect deviations from the idealized bond angle? a. CF4 b. NF3 c. OF2 d. H2S

Which species has the smaller bond angle, H3O+ or H2O ? Explain.

Which species has the smaller bond angle, ClO4 - or ClO3 - ? Explain

Determine the molecular geometry and sketch each molecule or ion using the bond conventions shown in the Representing Molecular Geometries on Paper box in Section 10.4 . a. SF4 b. CIF3 c. IF - 2 d. IBr -

Determine the molecular geometry and sketch each molecule or ion, using the bond conventions shown in the "Representing Molecular Geometries on Paper" Box in Section 10.4 . a. BrF5 b. SCl6 c. PF5 d. IF + 4

Determine the molecular geometry about each interior atom and sketch each molecule. a. C2H2 (skeletal structure HCCH) b. C2H4 (skeletal structure H2CCH2 ) c. C2H6 (skeletal structure H3CCH3 )

Determine the molecular geometry about each interior atom and sketch each molecule. a. N2 b. N2H2 (skeletal structure HNNH) c. N2H4 (skeletal structure H2NNH2 )

Each ball-and-stick model shows the electron and molecular geometry of a generic molecule. Explain what is wrong with each molecular geometry and provide the correct molecular geometry, given the number of lone pairs and bonding groups on the central atom

Each ball-and-stick model shows the electron and molecular geometry of a generic molecule. Explain what is wrong with each molecular geometry and provide the correct molecular geometry, given the number of lone pairs and bonding groups on the central atom.

Determine the geometry about each interior atom in each molecule and sketch the molecule. (Skeletal structure is indicated in parentheses.) a. CH3OH ( H3COH ) b. CH3OCH3 ( H3COCH3 ) c. H2O2 (HOOH)

Determine the geometry about each interior atom in each molecule and sketch the molecule. (Skeletal structure is indicated in parentheses.) a. CH3NH2 ( H3CNH2 ) b. CH3CO2CH3 ( H3CCOOCH3 both O atoms attached to second C) c. NH2CO2H ( H2NCOOH both O atoms attached to C)

Explain why CO2 and CCl4 are both nonpolar even though they contain polar bonds.

CH3F is a polar molecule, even though the tetrahedral geometry often leads to nonpolar molecules. Explain.

Determine whether each molecule in Exercise 35 is polar or nonpolar.

Determine whether each molecule in Exercise 36 is polar or nonpolar.

Determine whether each molecule is polar or nonpolar. a. ClO3 - b. SCl2 c. SCl4 d. BrCl5

Determine whether each molecule is polar or nonpolar. a. SiCl4 b. CF2Cl2 c. SeF6 d. IF5

The valence electron configurations of several atoms are shown next. How many bonds can each atom make without hybridization? a. Be 2s 2 b. P 3s 2 3p3 c. F 2s 2 2p5

The valence electron configurations of several atoms are shown next. How many bonds can each atom make without hybridization? a. B 2s 2 2p1 b. N 2s 2 2p3 c. O 2s 2 2p4

Write orbital diagrams (boxes with arrows in them) to represent the electron configurationswithout hybridizationfor all the atoms in PH3 . Circle the electrons involved in bonding. Draw a three-dimensional sketch of the molecule and show orbital overlap. What bond angle do you expect from the unhybridized orbitals? How well does valence bond theory agree with the experimentally measured bond angle of 93.3 ?

Write orbital diagrams (boxes with arrows in them) to represent the electron configurationswithout hybridizationfor all the atoms in SF2 . Circle the electrons involved in bonding. Draw a three-dimensional sketch of the molecule and show orbital overlap. What bond angle do you expect from the unhybridized orbitals? How well does valence bond theory agree with the experimentally measured bond angle of 98.2 ?

Write orbital diagrams (boxes with arrows in them) to represent the electron configuration of carbon before and after sp3 hybridization.

Write orbital diagrams (boxes with arrows in them) to represent the electron configurations of carbon before and after sp hybridization.

Which hybridization scheme allows the formation of at least one p bond? sp3 , sp2 , sp3 d2

Which hybridization scheme allows the central atom to form more than four bonds? \(s p^{3}, s p^{3} d, s p^{2}\)

Write a hybridization and bonding scheme for each molecule. Sketch the molecule, including overlapping orbitals, and label all bonds using the notation shown in Examples 10.6 and 10.7. a. \(\mathrm{CCl}_{4}\) b. \(\mathrm{NH}_{3}\) c. \(\mathrm{OF}_{2}\) d. \(\mathrm{CO}_{2}\)

Write a hybridization and bonding scheme for each molecule. Sketch the molecule, including overlapping orbitals, and label all bonds using the notation shown in Examples 10.6 and 10.7. a. \(CH_2 Br_2\) b. \(SO_2\) c. \(NF_3\) d. \(BF_3\)

Write a hybridization and bonding scheme for each molecule or ion. Sketch the structure, including overlapping orbitals, and label all bonds using the notation shown in Examples 10.6 and 10.7. a. \(\mathrm{COCl}_{2}\) (carbon is the central atom) b. \(\mathrm{BrF}_{5}\) c. \(\mathrm{XeF}_{2}\) d. \(\mathrm{I}_{3} \ ^-\)

Write a hybridization and bonding scheme for each molecule or ion. Sketch the structure, including overlapping orbitals, and label all bonds using the notation shown in Examples 10.6 and 10.7 . a. SO3 2- b. PF6 - c. BrF3 d. HCN

Write a hybridization and bonding scheme for each molecule that contains more than one interior atom. Indicate the hybridization about each interior atom. Sketch the structure, including overlapping orbitals, and label all bonds using the notation shown in Examples 10.6 and 10.7 . a. N2H2 (skeletal structure HNNH) b. N2H4 (skeletal structure H2NNH2 ) c. CH3NH2 (skeletal structure H3CNH2 )

Write a hybridization and bonding scheme for each molecule that contains more than one interior atom. Indicate the hybridization about each interior atom. Sketch the structure, including overlapping orbitals, and label all bonds using the notation shown in Examples 10.6 and 10.7 . a. C2H2 (skeletal structure HCCH) b. C2H4 (skeletal structure H2CCH2 ) c. C2H6 (skeletal structure H3CCH3 )

Consider the structure of the amino acid alanine. Indicate the hybridization about each interior atom.

Consider the structure of the amino acid aspartic acid. Indicate the hybridization about each interior atom.

. Sketch the bonding molecular orbital that results from the linear combination of two 1 s orbitals. Indicate the region where interference occurs and state the kind of interference (constructive or destructive).

Sketch the antibonding molecular orbital that results from the linear combination of two 1s orbitals. Indicate the region where interference occurs and state the kind of interference (constructive or destructive).

Draw an MO energy diagram and predict the bond order of Be + 2 and Be - 2 . Do you expect these molecules to exist in the gas phase?

Draw an MO energy diagram and predict the bond order of Li + 2 and Li - 2 . Do you expect these molecules to exist in the gas phase?

Sketch the bonding and antibonding molecular orbitals that result from linear combinations of the 2px atomic orbitals in a homonuclear diatomic molecule. (The 2px orbitals are those whose lobes are oriented along the bonding axis.)

Sketch the bonding and antibonding molecular orbitals that result from linear combinations of the 2pz atomic orbitals in a homonuclear diatomic molecule. (The 2pz orbitals are those whose lobes are oriented perpendicular to the bonding axis.) How do these molecular orbitals differ from those obtained from linear combinations of the 2py atomic orbitals? (The 2py orbitals are also oriented perpendicular to the bonding axis, but also perpendicular to the 2pz orbitals.)

Using the molecular orbital energy ordering for second-row homonuclear diatomic molecules in which the p2p orbitals lie at lower energy than the s2p, draw MO energy diagrams and predict the bond order in a molecule or ion with each number of total valence electrons. Will the molecule or ion be diamagnetic or paramagnetic? a. 4 b. 6 c. 8 d. 9

Using the molecular orbital energy ordering for second-row homonuclear diatomic molecules in which the p2p orbitals lie at higher energy than the s2p, draw MO energy diagrams and predict the bond order in a molecule or ion with each number of total valence electrons. Will the molecule or ion be diamagnetic or paramagnetic? a. 10 b. 12 c. 13 d. 14

Use molecular orbital theory to predict if each molecule or ion exists in a relatively stable form. a. H 2- 2 b. Ne2 c. He 2+ 2 d. F 2-

Use molecular orbital theory to predict if each molecule or ion exists in a relatively stable form. a. C 2+ 2 b. Li2 c. Be 2+ 2 d. Li 2-

According to MO theory, which molecule or ion has the highest bond order? Highest bond energy? Shortest bond length? \(\mathrm{C}_2,\mathrm{\ C}_2^{\ +},\mathrm{\ C}_2^{\ -}\)

According to MO theory, which molecule or ion has the highest bond order? Highest bond energy? Shortest bond length? O2, O2 -, O2 2-

Draw an MO energy diagram for CO. (Use the energy ordering of O2. ) Predict the bond order and make a sketch of the lowest energy bonding molecular orbital.

Draw an energy diagram for HCl. Predict the bond order and make a sketch of the lowest energy bonding molecular orbital.

For each compound, draw the Lewis structure, determine the geometry using VSEPR theory, determine whether the molecule is polar, identify the hybridization of all interior atoms, and make a sketch of the molecule, according to valence bond theory, showing orbital overlap. a. COF2 (carbon is the central atom) b. S2Cl2 (ClSSCl) c. SF4

For each compound, draw the Lewis structure, determine the geometry using VSEPR theory, determine whether the molecule is polar, identify the hybridization of all interior atoms, and make a sketch of the molecule, according to valence bond theory, showing orbital overlap. a. \(\mathrm{IF}_5\) b. \(\mathrm{CH}_2 \mathrm{CHCH}_3\) c. \(\mathrm{CH}_3 \mathrm{SH}\)

Amino acids are biological compounds that link together to form proteins, the workhorse molecules in living organisms. The skeletal structures of several simple amino acids are shown here. For each skeletal structure, complete the Lewis structure, determine the geometry and hybridization about each interior atom, and make a sketch of the molecule, using the bond conventions of Section 10.4 .

The genetic code is based on four different bases with the structures shown here. Assign a geometry and hybridization to each interior atom in these four bases. a. cytosine b. adenine c. thymine d. guanine

The structure of caffeine, present in coffee and many soft drinks, is shown here. How many pi bonds are present in caffeine? How many sigma bonds? Insert the lone pairs in the molecule. What kinds of orbitals do the lone pairs occupy?

The structure of acetylsalicylic acid (aspirin) is shown here. How many pi bonds are present in acetylsalicylic acid? How many sigma bonds? What parts of the molecule are free to rotate? What parts are rigid?

Most vitamins can be classified either as fat soluble, which results in their tendency to accumulate in the body (so that taking too much can be harmful), or water soluble, which results in their tendency to be quickly eliminated from the body in urine. Examine the structural formulas and space-filling models of these vitamins and determine whether each one is fat soluble (mostly nonpolar) or water soluble (mostly polar).

Water does not easily remove grease from dishes or hands, because grease is nonpolar and water is polar. The addition of soap to water, however, allows the grease to dissolve. Study the structure of sodium stearate (a soap) and describe how it works.

Draw a molecular orbital energy diagram for ClF. (Assume that the sp orbitals are lower in energy than the p orbitals.) What is the bond order in ClF?

Draw Lewis structures and MO diagrams for \(\mathrm{CN}^{+}\), CN, and \(\mathrm{CN}^{-}\). According to the Lewis model, which species is most stable? According to MO theory, which species is most stable? Do the two theories agree?

Bromine can form compounds or ions with any number of fluorine atoms from one to five. Write the formulas of all five of these species, assign a hybridization, and describe their electron and molecular geometry.

The compound C3H4 has two double bonds. Describe its bonding and geometry, using a valence bond approach.

Draw the structure of a molecule with the formula \(C_4 H_6 Cl_2\) that has a dipole moment of 0.

Draw the structures of two compounds that have the composition CH3NO2 and have all three H atoms bonded to the C. Predict which compound has the larger ONO bond angle.

How many hybrid orbitals do we use to describe each molecule? a. N2O5 b. C2H5NO (four C i H bonds and one O iH bond) c. BrCN (no formal charges)

Indicate which orbitals overlap to form the s bonds in the following. a. BeBr2 b. HgCl2 c. ICN

In VSEPR theory, which uses the Lewis model to determine molecular geometry, the trend of decreasing bond angle in CH4, NH3 , and H2O is accounted for by the greater repulsion of lone pair electrons compared to bonding pair electrons. How would this trend be accounted for in valence bond theory?

The results of a molecular orbital calculation for H2O are shown here. Examine each of the orbitals and classify them as bonding, antibonding, or nonbonding. Assign the correct number of electrons to the energy diagram. According to this energy diagram, is H2O stable? Explain.

The results of a molecular orbital calculation for NH3 are shown here. Examine each of the orbitals and classify them as bonding, antibonding, or nonbonding. Assign the correct number of electrons to the energy diagram. According to this energy diagram, is NH3 stable? Explain.

cis -2-Butene isomerizes to trans -2-butene via the reaction H H C C H H H H H H C C H C H C H H H H H H C C a. If isomerization requires breaking the bond, what minimum energy is required for isomerization in J>mol? In J>molecule? b. If the energy for isomerization came from light, what minimum frequency of light would be required? In what portion of the electromagnetic spectrum does this frequency lie?

The species NO2, NO + 2 , and NO - 2 in which N is the central atom, have very different bond angles. Predict what these bond angles might be with respect to the ideal angles and justify your prediction.

The bond angles increase steadily in the series PF3, PCl3, PBr3, and PI3. After consulting the data on atomic radii in Chapter 8 , provide an explanation for this observation.

The ion CH5 + can form under very special high-energy conditions in the vapor phase in a mass spectrometer. Propose a hybridization for the carbon atom and predict the geometry.

Neither the VSEPR model nor the hybridization model is able to account for the experimental observation that the F i Ba iF bond angle in gaseous BaF 2 is 108 rather than the predicted 180 . Suggest some possible explanations for this observation. 1

Draw the Lewis structure for acetamide (CH 3 CONH 2 ), an organic compound, and determine the geometry about each interior atom. Experiments show that the geometry about the nitrogen atom in acetamide is nearly planar. What resonance structure can account for the planar geometry about the nitrogen atom?

Use VSEPR to predict the geometry (including bond angles) about each interior atom of methyl azide (CH 3 N 3 ), and make a sketch of the molecule. Would you expect the bond angle between the two interior nitrogen atoms to be the same or different? Would you expect the two nitrogennitrogen bond lengths to be the same or different?

Which statement best captures the fundamental idea behind VSEPR theory? Explain what is wrong with each of the other statements. a. The angle between two or more bonds is determined primarily by the repulsions between the electrons within those bonds and other (lone pair) electrons on the central atom of a molecule. Each of these electron groups (bonding electrons or lone pair electrons) will lower its potential energy by maximizing its separation from other electron groups, thus determining the geometry of the molecule. b. The angle between two or more bonds is determined primarily by the repulsions between the electrons within those bonds. Each of these bonding electrons will lower its potential energy by maximizing its separation from other electron groups, thus determining the geometry of the molecule. c. The geometry of a molecule is determined by the shapes of the overlapping orbitals that form the chemical bonds. Therefore, to determine the geometry of a molecule, you must determine the shapes of the orbitals involved in bonding.

Suppose that a molecule has four bonding groups and one lone pair on the central atom. Suppose further that the molecule is confined to two dimensions (this is a purely hypothetical assumption for the sake of understanding the principles behind VSEPR theory). Make a sketch of the molecule and estimate the bond angles.

How does each of the three major bonding theories (the Lewis model, valence bond theory, and molecular orbital theory) define a single chemical bond? A double bond? A triple bond? How are these definitions similar? How are they different?

The most stable forms of the nonmetals in groups 4A, 5A, and 6A of the first period are molecules with multiple bonds. Beginning with the second period, the most stable forms of the nonmetals of these groups are molecules without multiple bonds. Propose an explanation for this observation based on valence bond theory.