Ch.8 - Basic Concepts of Chemical Bonding

Problem 95b

Chapter 8, Problem 95b

The following three Lewis structures can be drawn for N2O:
(b) The N—N bond length in N2O is 1.12 Å, slightly longer than a typical N≡N bond; and the N—O bond length is 1.19 Å, slightly shorter than a typical N═O bond (see Table 8.4). Based on these data, which resonance structure best represents N2O?

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Identify the possible resonance structures for N2O. These structures will involve different arrangements of single, double, and triple bonds between the nitrogen and oxygen atoms.

Consider the bond lengths given: N—N bond is 1.12 Å and N—O bond is 1.19 Å. Compare these lengths to typical bond lengths: a typical N≡N bond is shorter than 1.12 Å, and a typical N═O bond is longer than 1.19 Å.

Analyze each resonance structure to determine the type of bonds present between the atoms. For example, one structure might have a N≡N triple bond and a N—O single bond, while another might have a N═N double bond and a N═O double bond.

Evaluate which resonance structure aligns best with the given bond lengths. The structure with a N—N bond length slightly longer than a typical N≡N bond and a N—O bond length slightly shorter than a typical N═O bond is most representative.

Select the resonance structure that best matches the observed bond lengths, indicating the most accurate depiction of the electron distribution in N2O.

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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, which is crucial for understanding molecular geometry and reactivity. In the case of N2O, multiple Lewis structures can be drawn to depict different resonance forms, each contributing to the overall electronic structure of the molecule.

Resonance

Resonance refers to the concept that some molecules can be represented by two or more valid Lewis structures, known as resonance structures. These structures differ only in the arrangement of electrons, not in the arrangement of atoms. The actual structure of the molecule is a hybrid of these resonance forms, which helps explain properties such as bond lengths and strengths, as seen in the N—N and N—O bonds of N2O.

Bond Lengths

Bond length is the average distance between the nuclei of two bonded atoms. It is influenced by the type of bond (single, double, triple) and the atoms involved. In N2O, the bond lengths of N—N and N—O provide insight into the nature of the bonding and the stability of the resonance structures, indicating that the actual bond lengths are intermediate between those of typical N≡N and N═O bonds.

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Related Practice

Textbook Question

The triiodide ion, I3-, exists, whereas the corresponding ion with fluorine, F3-, does not. The I3- ion has a linear structure in which two outer I atoms are each bonded to a central I atom. Although I3- is a known ion, F3- is not.

c. Which of the following statements about the existence of I3- versus the nonexistence of F3- is or are true?

i. The Lewis structure of I3- shows 12 electrons around the central I atom.

ii. Elements from the second row of the periodic table generally do not form hypervalent molecules and ions.

iii. An I atom can form a hypervalent molecule or ion more readily than an F atom because of the larger size of the I atom.

Textbook Question

The hypochlorite ion, ClO^-, is the active ingredient in bleach. The perchlorate ion, ClO₄^-, is a main component of rocket propellants. Draw Lewis structures for both ions. (b) What is the formal charge of Cl in the perchlorate ion, assuming the Cl—O bonds are all single bonds?

Textbook Question

The following three Lewis structures can be drawn for N2O:

(a) Using formal charges, which of these three resonance forms is likely to be the most important?

Textbook Question

Mothballs are composed of naphthalene, C₁₀H₈, a molecule that consists of two six-membered rings of carbon fused along an edge, as shown in this incomplete Lewis structure:(a) Draw all of the resonance structures of naphthalene. How many are there?

Textbook Question

Mothballs are composed of naphthalene, C₁₀H₈, a molecule that consists of two six-membered rings of carbon fused along an edge, as shown in this incomplete Lewis structure:

(b) Do you expect the C—C bond lengths in the molecule to be similar to those of C—C single bonds, C ═C double bonds, or intermediate between C—C single and C ═C double bonds?

Textbook Question

Mothballs are composed of naphthalene, C₁₀H₈, a molecule that consists of two six-membered rings of carbon fused along an edge, as shown in this incomplete Lewis structure:

(c) Not all of the C—C bond lengths in naphthalene are equivalent. Based on your resonance structures, how many C—C bonds in the molecule do you expect to be shorter than the others?