Textbook Question
a) Using only the valence atomic orbitals of a hydrogenatom and a fluorine atom, and following the model ofFigure 9.46, how many MOs would you expect for the HFmolecule?
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Ch.9 - Molecular Geometry and Bonding Theories
Brown14th EditionChemistry: The Central ScienceISBN: 9780134414232
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Table of contents
- Ch.1 - Introduction: Matter, Energy, and Measurement140
- Ch.2 - Atoms, Molecules, and Ions192
- Ch.3 - Chemical Reactions and Reaction Stoichiometry172
- Ch.4 - Reactions in Aqueous Solution156
- Ch.5 - Thermochemistry151
- Ch.6 - Electronic Structure of Atoms137
- Ch.7 - Periodic Properties of the Elements127
- Ch.8 - Basic Concepts of Chemical Bonding143
- Ch.9 - Molecular Geometry and Bonding Theories167
- Ch.10 - Gases147
- Ch.11 - Liquids and Intermolecular Forces97
- Ch.12 - Solids and Modern Materials129
- Ch.13 - Properties of Solutions126
- Ch.14 - Chemical Kinetics175
- Ch.15 - Chemical Equilibrium107
- Ch.16 - Acid-Base Equilibria127
- Ch.17 - Additional Aspects of Aqueous Equilibria133
- Ch.18 - Chemistry of the Environment88
- Ch.19 - Chemical Thermodynamics140
- Ch.20 - Electrochemistry137
- Ch.21 - Nuclear Chemistry99
- Ch.22 - Chemistry of the Nonmetals66
- Ch.23 - Transition Metals and Coordination Chemistry69
- Ch.24 - The Chemistry of Life: Organic and Biological Chemistry11
Brown14th EditionChemistry: The Central ScienceISBN: 9780134414232Not the one you use?Change textbook
Chapter 9, Problem 112b
The energy-level diagram in Figure 9.36 shows that the sideways overlap of a pair of p orbitals produces two molecular orbitals, one bonding and one antibonding. In ethylene there is a pair of electrons in the bonding π orbital between the two carbons. Absorption of a photon of the appropriate wavelength can result in promotion of one of the bonding electrons from the p2p to the p*2p molecular orbital. (b) Assuming this electronic transition corresponds to the HOMO-LUMO transition, what is the LUMO in ethylene?
Verified step by step guidance1
Identify the Highest Occupied Molecular Orbital (HOMO) in ethylene, which is the bonding π orbital formed by the sideways overlap of p orbitals.
Determine the Lowest Unoccupied Molecular Orbital (LUMO) in ethylene, which is the antibonding π* orbital formed by the sideways overlap of p orbitals.
Understand that the HOMO-LUMO transition involves an electron being excited from the HOMO (bonding π orbital) to the LUMO (antibonding π* orbital).
Recognize that the LUMO in ethylene is the π*2p molecular orbital.
Conclude that the LUMO in ethylene is the antibonding π* orbital formed by the sideways overlap of the p orbitals.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Molecular Orbitals
Molecular orbitals (MOs) are formed when atomic orbitals combine during the bonding process. In the case of ethylene, the sideways overlap of p orbitals creates two types of MOs: bonding and antibonding. The bonding molecular orbital (π) is lower in energy and stabilizes the molecule, while the antibonding molecular orbital (π*) is higher in energy and destabilizes it. Understanding these orbitals is crucial for analyzing electronic transitions in molecules.
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Molecular Orbital Theory
HOMO and LUMO
The Highest Occupied Molecular Orbital (HOMO) and the Lowest Unoccupied Molecular Orbital (LUMO) are key concepts in molecular orbital theory. The HOMO is the highest energy orbital that contains electrons, while the LUMO is the lowest energy orbital that is empty. The transition of an electron from the HOMO to the LUMO upon photon absorption is fundamental in understanding the electronic properties of molecules, such as their reactivity and color.
Electronic Transitions
Electronic transitions refer to the movement of electrons between different energy levels or orbitals within a molecule. In ethylene, the absorption of a photon can promote an electron from the bonding π orbital (HOMO) to the antibonding π* orbital (LUMO). This transition is significant in spectroscopy and photochemistry, as it can lead to various chemical reactions and changes in molecular properties, such as color and stability.
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Related Practice
Textbook Question
(c) 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. Draw pictures showing the proper orientation of all three 2p orbitals on F interacting with a 1s orbital on H. Which of the 2p orbitals can actually make a bond with a 1s orbital, assuming that the atoms lie on the z-axis?
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Textbook Question
Sulfur tetrafluoride 1SF42 reacts slowly with O2 to form sulfur tetrafluoride monoxide 1OSF42 according to the following unbalanced reaction: SF41g2 + O21g2¡OSF41g2 The O atom and the four F atoms in OSF4 are bonded to a central S atom. (a) Balance the equation.
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Textbook Question
(b) How many of the MOs from part (a) would be occupied by electrons?