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Ch.8 - Basic Concepts of Chemical Bonding
All textbooksBrown 14th EditionCh.8 - Basic Concepts of Chemical BondingProblem 99a
Chapter 8, Problem 99a

Consider the molecule C4H5N, which has the connectivity shown below. (a) After the Lewis structure for the molecule is completed, how many s and how many p bonds are there in this molecule?
Lewis structure of C4H5N showing connectivity for bond analysis.

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1
Draw the Lewis structure for the molecule C4H5N, ensuring all atoms have complete octets (or duets for hydrogen).
Identify all single bonds (σ bonds) in the molecule. Each single bond represents one σ bond.
Identify any double or triple bonds in the molecule. Each double bond consists of one σ bond and one π bond, while each triple bond consists of one σ bond and two π bonds.
Count the total number of σ bonds in the molecule by summing the single bonds and the σ components of any double or triple bonds.
Count the total number of π bonds in the molecule by summing the π components of any double or triple bonds.

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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 how atoms are connected and the distribution of electrons, which is crucial for understanding molecular geometry and reactivity. In the case of C4H5N, drawing the Lewis structure allows us to identify the types of bonds present.
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Types of Chemical Bonds

Chemical bonds can be classified into two main types: sigma (σ) and pi (π) bonds. Sigma bonds are formed by the head-on overlap of atomic orbitals and are the first bonds formed between two atoms, while pi bonds result from the side-to-side overlap of p orbitals and are found in double and triple bonds. Understanding these bond types is essential for determining the total number of bonds in a molecule.
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Bond Counting

Counting bonds in a molecule involves identifying both the number of sigma and pi bonds present. Each single bond is a sigma bond, while double bonds consist of one sigma and one pi bond, and triple bonds contain one sigma and two pi bonds. This process is vital for answering questions about the bonding structure of C4H5N and determining the total number of s and p bonds.
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Related Practice
Textbook Question

Two compounds are isomers if they have the same chemical formula but different arrangements of atoms. Use Table 8.3 to estimate H for each of the following gas-phase isomerization reactions and indicate which isomer has the lower enthalpy. (d) Methyl isocyanide → Acetonitrile

Textbook Question

The Ti2 + ion is isoelectronic with the Ca atom. (b) Calculate the number of unpaired electrons for Ca and for Ti2+.

Textbook Question

The Ti2+ ion is isoelectronic with the Ca atom. (c) What charge would Ti have to be isoelectronic with Ca2+ ?

Textbook Question

(c) Hydrogen peroxide is sold commercially as an aqueous solution in brown bottles to protect it from light. Calculate the longest wavelength of light that has sufficient energy to break the weakest bond in hydrogen peroxide.

Textbook Question

The electron affinity of oxygen is -141 kJ/mol, corresponding to the reaction O(g) + e- → O-(g). The lattice energy of K2O(s) is 2238 kJ/mol. Use these data along with data in Appendix C and Figure 7.10 to calculate the 'second electron affinity' of oxygen, corresponding to the reaction O-(g) + e- → O2-(g)