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Ch.11 - Chemical Bonding II: Molecular Shapes, VSEPR & MO Theory
Tro - Chemistry: A Molecular Approach 6th Edition
Tro6th EditionChemistry: A Molecular ApproachISBN: 9780137832217Not the one you use?Change textbook
All textbooksTro 6th EditionCh.11 - Chemical Bonding II: Molecular Shapes, VSEPR & MO TheoryProblem 84a
Chapter 11, Problem 84a

According to MO theory, which molecule or ion has the highest bond order? O2, O2- , O22-

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Identify the molecular orbitals involved in the bonding of O_2 and its ions. For O_2, the relevant molecular orbitals are: \( \sigma_{2s}, \sigma^*_{2s}, \sigma_{2p_z}, \pi_{2p_x} = \pi_{2p_y}, \pi^*_{2p_x} = \pi^*_{2p_y}, \sigma^*_{2p_z} \).
Determine the electron configuration for each species: O_2, O_2^-, and O_2^{2-}. O_2 has 12 valence electrons, O_2^- has 13, and O_2^{2-} has 14.
Calculate the bond order using the formula: \( \text{Bond Order} = \frac{1}{2} (\text{Number of bonding electrons} - \text{Number of antibonding electrons}) \).
For O_2, fill the molecular orbitals with 12 electrons and calculate the bond order. For O_2^-, add one more electron to the antibonding \( \pi^* \) orbitals and calculate the bond order. For O_2^{2-}, add two more electrons to the antibonding \( \pi^* \) orbitals and calculate the bond order.
Compare the bond orders of O_2, O_2^-, and O_2^{2-} to determine which has the highest bond order.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Molecular Orbital Theory (MO Theory)

Molecular Orbital Theory describes the behavior of electrons in molecules, where atomic orbitals combine to form molecular orbitals that can be occupied by electrons. This theory allows for the prediction of bond order, stability, and magnetic properties of molecules based on the arrangement of electrons in these orbitals.
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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 and greater stability of the molecule.
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Electron Configuration in Diatomic Molecules

The electron configuration of diatomic molecules, such as O2 and its ions, is crucial for determining their bond order. For O2, the configuration is (σ2s)²(σ*2s)²(σ2p)²(π2p)⁴(π*2p)², which helps in calculating the bond order. The addition or removal of electrons in ions like O2- and O2²- alters this configuration and thus affects the bond order.
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