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Ch.10 - Chemical Bonding II: Molecular Shapes & Valence Bond Theory
All textbooksTro 4th EditionCh.10 - Chemical Bonding II: Molecular Shapes & Valence Bond TheoryProblem 56
Chapter 10, Problem 56

Write orbital diagrams (boxes with arrows in them) to represent the electron configurations—without hybridization—for all the atoms in SF2. Circle the electrons involved in bonding. Draw a three-dimensional sketch of the molecule and show orbital overlap. What bond angle do you expect from the unhybridized orbitals? How well does valence bond theory agree with the experimentally measured bond angle of 98.2° ?

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Identify the electron configurations for sulfur (S) and fluorine (F). Sulfur has an atomic number of 16, so its electron configuration is 1s² 2s² 2p⁶ 3s² 3p⁴. Fluorine, with an atomic number of 9, has the electron configuration 1s² 2s² 2p⁵.
Draw the orbital diagrams for sulfur and fluorine. For sulfur, fill the 1s, 2s, and 2p orbitals completely, and place four electrons in the 3p orbital. For fluorine, fill the 1s, 2s orbitals completely, and place five electrons in the 2p orbital. Use arrows to represent electrons, with up and down arrows indicating opposite spins.
Circle the electrons in the outermost orbitals of sulfur and fluorine that are involved in bonding. In sulfur, this will be the two unpaired electrons in the 3p orbital. In fluorine, it will be one unpaired electron in the 2p orbital.
Draw a three-dimensional sketch of the SF2 molecule. Show sulfur at the center with two fluorine atoms bonded to it. Indicate the overlap of the unpaired electrons in the sulfur 3p orbitals with the unpaired electrons in the fluorine 2p orbitals to form sigma bonds.
Discuss the expected bond angle in SF2 based on the p-orbital overlap in the valence bond theory, which would predict angles close to 90° due to the p-orbital orientations. Compare this with the experimentally measured bond angle of 98.2°, and explain that the slight deviation might be due to factors like lone pair repulsion affecting the bond angles.

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Key Concepts

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

Orbital Diagrams

Orbital diagrams visually represent the distribution of electrons in an atom's orbitals. Each box corresponds to an orbital, and arrows indicate the presence of electrons, with their direction showing spin. These diagrams help in understanding electron configurations and the pairing of electrons, which is crucial for predicting bonding behavior in molecules.
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Valence Bond Theory

Valence Bond Theory (VBT) explains how atoms bond by overlapping their atomic orbitals to form covalent bonds. It emphasizes the role of unhybridized orbitals in determining molecular geometry and bond angles. In the case of SF2, VBT can be used to predict the bond angle based on the arrangement of the unhybridized orbitals, which is essential for comparing theoretical predictions with experimental data.
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Bond Angles and Molecular Geometry

Bond angles are the angles between adjacent bonds in a molecule, which are influenced by the arrangement of electron pairs around a central atom. In SF2, the expected bond angle is affected by the presence of lone pairs and the repulsion between bonding and non-bonding electron pairs. Understanding these angles is crucial for predicting molecular shape and comparing theoretical predictions with experimental measurements.
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Related Practice
Textbook Question

The valence electron configurations of several atoms are shown here. How many bonds can each atom make without hybridization? a. B 2s22p1 b. N 2s22p3

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Textbook Question

The valence electron configurations of several atoms are shown here. How many bonds can each atom make without hybridization? c. O 2s22p4

Textbook Question

Write orbital diagrams (boxes with arrows in them) to represent the electron configuration of carbon before and after sp3 hybridization.

Textbook Question

Write orbital diagrams (boxes with arrows in them) to represent the electron configurations of carbon before and after sp hybridization.

Textbook Question

Which hybridization scheme allows the formation of at least one p bond? sp3, sp2, sp3d2