Textbook Question
Determine the electron configurations for CN+, CN, and CN-. (a) Which species has the strongest C¬N bond?
Ch.9 - Molecular Geometry and Bonding Theories
Chapter 9, Problem 83a
Assume that the MOs of diatomics from the third row of the periodic table, such as P2, 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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Identify the valence atomic orbitals of a phosphorus (P) atom. Phosphorus is in the third period and has the electron configuration [Ne] 3s^2 3p^3.
Recognize that the valence atomic orbitals involved in bonding are the 3s and 3p orbitals.
Understand that in diatomic molecules like P2, these valence orbitals combine to form molecular orbitals (MOs).
Note that the 3s orbitals from each phosphorus atom will combine to form sigma (\(\sigma\)) bonding and antibonding MOs.
The 3p orbitals will combine to form both sigma (\(\sigma\)) and pi (\(\pi\)) bonding and antibonding MOs, similar to the MO formation in second-row diatomics.
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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 MOs can be bonding, antibonding, or non-bonding, depending on the phase relationship of the combining atomic orbitals. Understanding how MOs are constructed is crucial for predicting the electronic structure and properties of molecules like P2.
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Molecular Orbital Theory
Valence Atomic Orbitals
Valence atomic orbitals are the outermost orbitals of an atom that participate in chemical bonding. For phosphorus (P), the relevant valence orbitals include the 3s and 3p orbitals. Identifying which of these orbitals contribute to the formation of MOs in diatomic molecules is essential for understanding their bonding characteristics and molecular geometry.
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Periodic Trends in Orbital Energy
The energy levels of atomic orbitals vary across periods in the periodic table, influencing the formation of MOs. As you move from the second to the third row, the energy of the 3s and 3p orbitals in phosphorus is higher than that of the corresponding 2s and 2p orbitals in second-row elements. This trend affects the overlap and interaction of orbitals when forming MOs, which is key to understanding the bonding in P2.
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Related Practice
Textbook Question
Determine the electron configurations for CN+, CN, and CN-. b. Which species, if any, is paramagnetic?
Textbook Question
(c) With what neutral homonuclear diatomic molecules are the NO+ and NO- ions isoelectronic (same number of electrons)? With what neutral homonuclear diatomic molecule is the NO- ion isoelectronic (same number of electrons)?
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Textbook Question
Assume that the MOs of diatomics from the third row of the periodic table, such as P2, are analogous to those from the second row.
c. For the P2 molecule, how many electrons occupy the MO in the figure?
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. (a) Which valence atomic orbitals of I and of Br are used to construct the MOs of IBr?
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. Determine whether each of the following statements about this orbital is true: i. This is an antibonding orbital. ii. The larger contribution is from the I atom. iii. The energy of the molecular orbital is closer in energy to the valence atomic orbitals of Br than to those of I.