Textbook Question
Indicate whether each statement is true or false. (c) Molecules containing electrons that occupy antibonding orbitals must be unstable.
Ch.9 - Molecular Geometry and Bonding Theories
Chapter 9, Problem 76
Explain the following: (c) The O22 + ion has a stronger O—O bond than O2 itself.
Verified step by step guidance1
Understand the electronic configuration of O2 and O2^2+: O2 has 16 electrons and is a diradical with two unpaired electrons in its molecular orbitals, which weakens the bond. O2^2+ (peroxide ion), having lost two electrons, results in 14 electrons with paired spins, leading to a more stable electronic configuration.
Recognize the bond order concept: Bond order is a measure of the number of chemical bonds between a pair of atoms. In molecular orbital theory, bond order is half the difference between the number of bonding and antibonding electrons. Higher bond order corresponds to a stronger bond.
Calculate the bond order for both O2 and O2^2+: For O2, the bond order is 2 (indicating a double bond), and for O2^2+, the bond order increases due to the loss of antibonding electrons, which strengthens the bond.
Relate bond strength to bond length: Generally, a higher bond order correlates with a shorter and stronger bond. Since O2^2+ has a higher bond order than O2, the O—O bond in O2^2+ is stronger and shorter than in O2.
Apply molecular orbital theory to explain stability: The removal of electrons from antibonding orbitals in O2^2+ leads to a reduction in electron-electron repulsion within the molecule, which contributes to the increased stability and strength of the O—O bond in O2^2+ compared to O2.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Bond Order
Bond order is a measure of the number of chemical bonds between a pair of atoms. It is calculated as the difference between the number of bonding and antibonding electrons divided by two. A higher bond order indicates a stronger bond, as seen in the O2 molecule, which has a bond order of 2, while the O22+ ion has a bond order of 3, suggesting a stronger O—O bond.
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Average Bond Order
Molecular Orbital Theory
Molecular Orbital (MO) theory describes the electronic structure of molecules by considering the combination of atomic orbitals to form molecular orbitals. In the case of O2 and O22+, the removal of electrons from antibonding orbitals in O22+ leads to a greater stabilization of the bonding orbitals, resulting in a stronger O—O bond compared to the neutral O2 molecule.
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Electron Configuration
Electron configuration refers to the distribution of electrons in an atom or ion's orbitals. For O2, the electron configuration includes two unpaired electrons in antibonding orbitals, while O22+ has fewer electrons, leading to a more stable configuration. This reduction in electron repulsion in O22+ contributes to the increased strength of the O—O bond compared to O2.
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Related Practice
Textbook Question
Indicate whether each statement is true or false. (d) Electrons cannot occupy a nonbonding orbital.
Textbook Question
How would we describe a substance that contains only paired electrons and is weakly repelled by a magnetic field? Which of the following ions would you expect to possess similar characteristics: H2-, Ne2+, F2, O22 +?
Textbook Question
Using Figures 9.35 and 9.43 as guides, draw the molecular orbital electron configuration for (d) Ne22 +. In each case indicate whether the addition of an electron to the ion would increase or decrease the bond order of the species.
Textbook Question
If we assume that the energy-level diagrams for homonuclear diatomic molecules shown in Figure 9.43 can be applied to heteronuclear diatomic molecules and ions, predict the bond order and magnetic behavior of (b) NO+.