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Ch.9 - Molecular Geometry and Bonding Theories
Chapter 9, Problem 98a

The molecule C4H5N has the connectivity shown here. a. After the Lewis structure for the molecule is completed, how many 𝜎 and how many πœ‹ bonds are there in this molecule?

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Step 1: Draw the Lewis structure for C4H5N. Start by arranging the atoms according to the given connectivity.
Step 2: Count the total number of valence electrons available. Carbon (C) has 4 valence electrons, hydrogen (H) has 1, and nitrogen (N) has 5.
Step 3: Distribute the electrons to form bonds between the atoms, ensuring each atom satisfies the octet rule where applicable.
Step 4: Identify the types of bonds formed. A single bond is a sigma (𝜎) bond, while a double bond consists of one sigma (𝜎) and one pi (πœ‹) bond.
Step 5: Count the total number of sigma (𝜎) and pi (πœ‹) bonds in the completed Lewis structure.

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Key Concepts

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

Lewis Structures

Lewis structures are diagrams that represent the bonding between atoms in a molecule and the lone pairs of electrons that may exist. They help visualize the arrangement of electrons and the connectivity of atoms, allowing chemists to predict molecular geometry and reactivity. Understanding how to draw and interpret Lewis structures is essential for identifying the types of bonds present in a molecule.
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Sigma (𝜎) and Pi (πœ‹) Bonds

Sigma (𝜎) bonds are the first bonds formed between two atoms, created by the head-on overlap of atomic orbitals. Pi (πœ‹) bonds, on the other hand, are formed by the side-to-side overlap of p orbitals and are present in double and triple bonds alongside sigma bonds. Recognizing the difference between these bond types is crucial for determining the total number of each in a given molecule.
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Bond Counting

Bond counting involves identifying and quantifying the different types of bonds in a molecule after constructing its Lewis structure. This process includes counting the number of sigma and pi bonds, which is important for understanding the molecule's stability, reactivity, and overall structure. Accurate bond counting is essential for answering questions related to molecular composition and behavior.
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