The iodine bromide molecule, IBr, is an interhalogen compound. Assume that the molecular orbitals of IBr are analogous to the homonuclear diatomic molecule F2. (a) Which valence atomic orbitals of I and of Br are used to construct the MOs of IBr?

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Identify the valence atomic orbitals for iodine (I) and bromine (Br). Both I and Br are in Group 17 of the periodic table, so they have similar valence electron configurations.

For iodine (I), the valence electrons are in the 5th shell, specifically in the 5s and 5p orbitals. Therefore, the valence atomic orbitals are 5s and 5p.

For bromine (Br), the valence electrons are in the 4th shell, specifically in the 4s and 4p orbitals. Therefore, the valence atomic orbitals are 4s and 4p.

Construct the molecular orbitals (MOs) of IBr by combining the valence atomic orbitals of I and Br. The s orbitals will combine to form sigma (σ) and sigma star (σ*) MOs, while the p orbitals will combine to form sigma (σ), sigma star (σ*), pi (π), and pi star (π*) MOs.

Consider the energy levels of the atomic orbitals. Since iodine is less electronegative than bromine, its atomic orbitals will be higher in energy compared to those of bromine. This will affect the energy ordering of the resulting molecular orbitals.

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Key Concepts

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

Molecular Orbitals (MOs)

Molecular orbitals are formed by the linear combination of atomic orbitals (LCAO) from the constituent atoms in a molecule. In diatomic molecules, these orbitals can be bonding, antibonding, or non-bonding, influencing the molecule's stability and properties. Understanding how atomic orbitals combine to form MOs is crucial for predicting the behavior of molecules like IBr.

Atomic Orbitals of Iodine and Bromine

Iodine (I) and bromine (Br) are both halogens with similar electronic configurations. Iodine has the electron configuration [Kr] 4d10 5s2 5p5, while bromine is [Ar] 4s2 4p5. The valence atomic orbitals involved in forming MOs for IBr are primarily the 5p orbitals of iodine and the 4p orbitals of bromine, which overlap to create the molecular orbitals.

Interhalogen Compounds

Interhalogen compounds are molecules formed from two different halogens. They exhibit unique properties that differ from those of homonuclear diatomic molecules, such as F2. Understanding the nature of interhalogen compounds, including their bond characteristics and molecular geometry, is essential for analyzing the molecular orbitals of IBr and predicting its behavior.

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Consider the molecular orbitals of the P2 molecule. Assume that the MOs of diatomics from the third row of the periodic table are analogous to those from the second row. (a) Which valence atomic orbitals of P are used to construct the MOs of P2?

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Consider the molecular orbitals of the P2 molecule. Assume that the MOs of diatomics from the third row of the periodic table are analogous to those from the second row. (c) For the P2 molecule, how many electrons occupy the MO in the figure?

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Textbook Question

The iodine bromide molecule, IBr, is an interhalogen compound. Assume that the molecular orbitals of IBr are analogous to the homonuclear diatomic molecule F2. (c) One of the valence MOs of IBr is sketched here. Why are the atomic orbital contributions to this MO different in size?

Textbook Question

An AB2 molecule is described as having a tetrahedral geometry. (a) How many nonbonding domains are on atom A?

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