Ch.10 - Molecular Shapes & Valence Bond TheoryWorksheetSee all chapters
All Chapters
Ch.1 - Intro to General Chemistry
Ch.2 - Atoms & Elements
Ch.3 - Chemical Reactions
BONUS: Lab Techniques and Procedures
BONUS: Mathematical Operations and Functions
Ch.4 - Chemical Quantities & Aqueous Reactions
Ch.5 - Gases
Ch.6 - Thermochemistry
Ch.7 - Quantum Mechanics
Ch.8 - Periodic Properties of the Elements
Ch.9 - Bonding & Molecular Structure
Ch.10 - Molecular Shapes & Valence Bond Theory
Ch.11 - Liquids, Solids & Intermolecular Forces
Ch.12 - Solutions
Ch.13 - Chemical Kinetics
Ch.14 - Chemical Equilibrium
Ch.15 - Acid and Base Equilibrium
Ch.16 - Aqueous Equilibrium
Ch. 17 - Chemical Thermodynamics
Ch.18 - Electrochemistry
Ch.19 - Nuclear Chemistry
Ch.20 - Organic Chemistry
Ch.22 - Chemistry of the Nonmetals
Ch.23 - Transition Metals and Coordination Compounds
Molecular Orbital Diagrams

molecular orbital diagram explains chemical bonds within molecules based on the union of atomic orbials. 

Concept #1: A heteronuclear diatomic molecule is composed of two different elements covalently bonded together.

Concept #2: There are some key similarities and differences when comparing heteronuclear and homonuclear diatomic molecules. 

Example #1: Using your knowledge of molecular orbital diagrams, determine the bond order of the NO- ion. 

Additional Problems
Which of the following mixtures of atomic orbitals best describes the σ bonding orbitals in HeH+?   a. s + s b. s – s c. pz + pz d. px – pz e. px + py
Use the molecular orbital energy diagram below for the next three questions. How many unpaired electrons are in O 2+? a. 0       b. 1       c. 2       d. 3     What is the bond order of OF? a. 0       b. ½       c. 1       d. 1 ½       e. 2     Which of the following is not paramagnetic? a. O 2+       b. OF       c. NO       d. OF –       e. CO+
Utilize the molecular orbital diagram below to answer the following questions.   How many electrons are present in antibonding molecular orbitals?  (a) 2     (b) 4     (c) 6     (d) 8     (e) 10   What is the bond order for the molecule? (a) 3     (b) 2.5     (c) 2     (d) 1.5     (e) 1   What is the most likely formula for the molecule represented in the molecular orbital diagram? (a) O22−     (b) ONe     (c) ONe +     (d) OF     (e) OF +    
Use the molecular orbital diagram to figure out the electronic configuration for CN. Which of the following statements is correct? a) CN is diamagnetic. b) CN− is paramagnetic. c) If an electron is removed to give CN+, the bond order increases. d) The π*2p orbital is the highest energy orbital containing an electron in CN e) If an electron is added to give CN−, the bond length decreases.  
Draw the MO energy diagram for CO on your own, then use it to predict the bond order for the molecule. (Use the energy ordering of O2. )
The diagram shows the highest occupied MOs of a neutral molecule CX, where element X is in the same row of the periodic table as C.Based on the number of electrons, can you determine the identity of X?
The energy-level diagram for atomic and molecular orbitals in NO.How many valence-shell electrons are there in NO?
Using only the valence atomic orbitals of a hydrogen atom and a fluorine atom, how many MOs would you expect for the HF molecule?
It turns out that the difference in energies between the valence atomic orbitals of H and F are sufficiently different that we can neglect the interaction of the 1s orbital of hydrogen with the 2s orbital of fluorine. The 1s orbital of hydrogen will mix only with one 2p orbital of fluorine. With the help of pictures showing the proper orientation of all three 2p orbitals on F interacting with a 1s orbital on H, determine which of the 2p orbitals can actually make a bond with a 1s orbital, assuming that the atoms lie on the z-axis?
Do you think the MO diagram shown in Figure 9.46 in the textbook could be used to describe the MOs of the HF molecule?
Complete this molecular orbital diagram for CN– then determine the bond order. Note that the 1s orbital is not shown in this problem.
Which of the following is false?a. KCl is a heteronuclear diatomic moleculeb. H2S is called hydrogen sulfide as a molecule and called hydrosulfuric acid as an acidc. HCl is called hydrogen chloride as a molecule and called hydrochloric acid as an acidd. H2 is a homonuclear diatomic molecule but is not a compounde. NO2 is called nitrogen dioxide and N2O is called dinitrogen monoxidef. H2O is a heteronuclear polyatomic molecule and also a compoundg. HCl is a heteronuclear diatomic molecule and also a compound
Is CO paramagnetic or diamagnetic?
The nitric oxide molecule, NO, readily loses one electron to form the NO + ion. Why is this consistent with the electronic structure of NO?
Complete this molecular orbital diagram for CN– then determine the bond order. Note that the 1s orbital is not shown in this problem.
If CO gained one election, becoming CO -, would the bond become weaker or stronger?
Draw the MO energy diagram for HCl on your own, then use it to predict the bond order for the molecule.
You may want to reference (Pages 369 - 371) Section 9.7 while completing this problem.The following is part of a molecular orbital energy-level diagram for MOs constructed from 1s atomic orbitals.For which of the following molecules or ions could this be the energy-level diagram: H2, He2, H2+, He2+, or H2–?
Use the drawing of a molecular orbital energy diagram for ClF (assume that the σp orbitals are lower in energy than the π pi orbitals) to predict the bond order?
You may want to reference (Pages 426 - 461) Chapter 10 while completing this problem.Draw Lewis structures for CN+, CN, and CN–. According to MO theory, which species is most stable?
You may want to reference(Pages 371 - 382)Section 9.8 while completing this problem.If we assume that the energy-level diagrams for homonuclear diatomic molecules shown in Figure 9.42 in the textbook can be applied to heteronuclear diatomic molecules and ions, predict the bond order and magnetic behavior of each: (a) CO+, (b) NO–, (c) OF+, (d) NeF+.
Determine the electron configurations for CN+, CN, and CN–. Which species has the strongest C–N bond?
Determine the electron configurations for CN+, CN, and CN–. Which species, if any, has unpaired electrons?
The diatomic molecule OH exists in the gas phase. The bond length and bond energy have been measured to be 97.06 pm and 424.7 kJ/mol, respectively. Assume that the OH molecule is analogous to the HF molecule discussed in the chapter and that molecular orbitals result from the overlap of a lowerenergy pz orbital from oxygen with the higher-energy 1s orbital of hydrogen (the O—H bond lies along the z-axis). a. Which of the two molecular orbitals will have the greater hydrogen 1s character?
The diatomic molecule OH exists in the gas phase. The bond length and bond energy have been measured to be 97.06 pm and 424.7 kJ/mol, respectively. Assume that the OH molecule is analogous to the HF molecule discussed in the chapter and that molecular orbitals result from the overlap of a lowerenergy pz orbital from oxygen with the higher-energy 1s orbital of hydrogen (the O—H bond lies along the z-axis). c. Knowing that only the 2p orbitals of oxygen will interact significantly with the 1s orbital of hydrogen, complete the molecular orbital energy-level diagram for OH. Place the correct number of electrons in the energy levels.
Use Figs. 4‑54 and 4‑55 to answer the following questions.a. Would the bonding molecular orbital in HF place greater electron density near the H or the F atom? Why?
Use Figs. 4‑54 and 4‑55 to answer the following questions.b. Would the bonding molecular orbital have greater fluorine 2p character, greater hydrogen 1s character, or an equal contribution from both? Why?
Use Figs. 4‑54 and 4‑55 to answer the following questions.a. Would the bonding molecular orbital in HF place greater electron density near the H or the F atom? Why?b. Would the bonding molecular orbital have greater fluorine 2p character, greater hydrogen 1s character, or an equal contribution from both? Why?c. Answer the previous two questions for the antibonding molecular orbital in HF.
The ionosphere lies about 100 km above Earth’s surface. This layer of the atmosphere consists mostly of NO, O2, and N2, and photoionization creates NO +, O 2+, and N 2+. Use MO theory to compare the bond orders of the molecules and ions.
The ionosphere lies about 100 km above Earth’s surface. This layer of the atmosphere consists mostly of NO, O2, and N2, and photoionization creates NO +, O 2+, and N 2+. Does the magnetic behavior of each species change when its ion forms?
In terms of the molecular orbital model, which species in each of the following two pairs will most likely be the one to gain an electron? Explain.a. CN or NO
You may want to reference (Pages 372 - 382) Section 9.8 while completing this problem.The nitric oxide molecule, NO, readily loses one electron to form the NO+ ion. Which of the following is the best explanation of why this happens?(i) Oxygen is more electronegative than nitrogen.(ii) The highest energy electron in NO lies in a π*2p molecular orbital.(iii) The π*2p MO in NO is completely filled.
Using the molecular orbital model, write electron configurations for the following diatomic species and calculate the bond orders. Which ones are paramagnetic? Place the species in order of increasing bond length and bond energy.a. CN + b. CN c. CN -
Using the molecular orbital model, write electron configurations for the following diatomic species and calculate the bond orders. Which ones are paramagnetic? Place the species in order of increasing bond length and bond energy.a. CO b. CO+ c. CO2+
The transport of O2 in the blood is carried out by hemoglobin. Carbon monoxide can interfere with oxygen transport because hemoglobin has a stronger affinity for CO than for O2. If CO is present, normal uptake of O2 is prevented, depriving the body of needed oxygen. Using the molecular orbital model, write the electron configurations for CO and for O2. From your configurations, give two property differences between CO and O2.
Carbon monoxide, CO, is isoelectronic to N2. Draw a Lewis structure for CO that satisfies the octet rule.Assume that the diagram in Figure 9.46 can be used to describe the MOs of CO. What is the predicted bond order for CO? Is this answer in accord with the Lewis structure you drew?
Carbon monoxide, CO, is isoelectronic to N2. Experimentally, it is found that the highest-energy electrons in CO reside in a sigma { m{ - }}{ m{type}} MO. Is that observation consistent with Figure 9.46?If not, what modification needs to be made to the diagram? How does this modification relate to Figure 9.43?
Carbon monoxide, CO, is isoelectronic to N2. Would you expect the π2p MOs of CO to have equal atomic orbital contributions from the C and O atoms? If not, which atom would have the greater contribution?
The diagram shows the highest occupied MOs of a neutral molecule CX, where element X is in the same row of the periodic table as C.Would the molecule be diamagnetic or paramagnetic?
The diagram shows the highest occupied MOs of a neutral molecule CX, where element X is in the same row of the periodic table as C.Consider the π2p MOs of the molecule. Would you expect them to have a greater atomic orbital contribution from C, have a greater atomic orbital contribution from X, or be an equal mixture of atomic orbitals from the two atoms?
Molecular nitrogen, carbon monoxide, and cyanide ion are isoelectronic. Draw an MO diagram for each.
Molecular nitrogen, carbon monoxide, and cyanide ion are isoelectronic. CO and CN − are toxic. What property may explain why N2 isn’t?
Draw the orbital diagram for carbon in CO 2 showing how many carbon atom electrons are in each orbital.
Using only the valence atomic orbitals of a hydrogen atom and a fluorine atom, and following the model, how many MOs would you expect for the HF molecule? How many of the MOs would be occupied by electrons?
Apply molecular orbital theory to determine the bond order of NO. (Use the energy ordering of O2.)
Use molecular orbital theory to predict whether or not each of the following molecules or ions should exist in a relatively stable form.a. C22+b. Li2c. Be22+d. Li22–
In which of the following diatomic molecules would the bond strength be expected to weaken as an electron is removed?a. H2 b. B2c. C22-d. OF