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Ch.9 - Molecular Geometry and Bonding Theories
Brown - Chemistry: The Central Science 15th Edition
Brown15th EditionChemistry: The Central ScienceISBN: 9780137542970Not the one you use?Change textbook
All textbooksBrown 15th EditionCh.9 - Molecular Geometry and Bonding TheoriesProblem 7d
Chapter 9, Problem 7d

Consider the following hydrocarbon:
d. Identify all the 120° bond angles in the molecule.

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1
Identify the type of hydrocarbon given in the problem.
Recognize that 120° bond angles are characteristic of sp2 hybridized carbon atoms.
Determine which carbon atoms in the molecule are sp2 hybridized.
Look for carbon atoms that are part of double bonds or are in a trigonal planar geometry.
List all the bond angles around these sp2 hybridized carbon atoms that are 120°.

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Key Concepts

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

Molecular Geometry

Molecular geometry refers to the three-dimensional arrangement of atoms within a molecule. It is determined by the number of bonding pairs and lone pairs of electrons around the central atom, which influences the angles between bonds. Understanding molecular geometry is crucial for predicting bond angles, such as the 120° angles typically found in trigonal planar structures.
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VSEPR Theory

Valence Shell Electron Pair Repulsion (VSEPR) theory is a model used to predict the geometry of individual molecules based on the repulsion between electron pairs. According to VSEPR, electron pairs will arrange themselves to minimize repulsion, leading to specific bond angles. In hydrocarbons with trigonal planar geometry, the bond angles are approximately 120° due to the arrangement of three bonding pairs around a central atom.
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Hybridization

Hybridization is the concept of mixing atomic orbitals to form new hybrid orbitals that can accommodate bonding. In the case of hydrocarbons with 120° bond angles, sp² hybridization occurs, where one s orbital and two p orbitals combine to form three equivalent sp² hybrid orbitals. This hybridization explains the planar structure and the specific bond angles observed in such molecules.
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Related Practice
Textbook Question

Consider the following hydrocarbon:

a. What is the hybridization at each carbon atom in the molecule?

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Textbook Question

The following is part of a molecular orbital energy-level diagram for MOs constructed from 1s atomic orbitals.

(a) What labels do we use for the two MOs shown?

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Textbook Question

The drawing below shows the overlap of two hybrid orbitals to form a bond in a hydrocarbon. (a) Which of the following types of bonds is being formed: (i) C¬C s, (ii) C¬C p, or (iii) C¬H s?

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Textbook Question

The drawing below shows the overlap of two hybrid orbitals to form a bond in a hydrocarbon. (b) Which of the following could be the identity of the hydrocarbon: (i) CH4, (ii) C2H6, (iii) C2H4, or (iv) C2H2?

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Textbook Question

The orbital diagram that follows presents the final step in the formation of hybrid orbitals by a silicon atom. (b) What type of hybrid orbital is produced in this hybridization?

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Textbook Question

Consider the following hydrocarbon:

b. How many 𝜎 bonds are there in the molecule?

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