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Ch.1 - Structure and Bonding
Wade - Organic Chemistry 9th Edition
Wade9th EditionOrganic ChemistryISBN: 9780135213728Not the one you use?Change textbook
All textbooksWade 9th EditionCh.1 - Structure and BondingProblem 52a
Chapter 1, Problem 52a

For each of the following compounds and ions,
1. Draw a Lewis structure.
2. Show the kinds of orbitals that overlap to form each bond.
3. Give approximate bond angles around each atom except hydrogen.
a. [NH2]–

Verified step by step guidance
1
Step 1: Draw the Lewis structure for the [NH2]- ion. Start by counting the total number of valence electrons. Nitrogen (N) has 5 valence electrons, and each hydrogen (H) has 1 valence electron. The negative charge indicates an additional electron, giving a total of 8 valence electrons.
Step 2: Arrange the atoms with nitrogen as the central atom. Place the two hydrogen atoms around nitrogen and distribute the electrons to satisfy the octet rule for nitrogen. Each hydrogen will form a single bond with nitrogen, using 2 electrons per bond.
Step 3: Assign the remaining electrons as lone pairs on the nitrogen atom. After forming two N-H bonds, 4 electrons are used, leaving 4 electrons to be placed as two lone pairs on nitrogen.
Step 4: Identify the types of orbitals involved in bonding. The N-H bonds are formed by the overlap of the sp3 hybrid orbitals of nitrogen with the 1s orbitals of hydrogen.
Step 5: Determine the approximate bond angles. The [NH2]- ion has a bent shape due to the lone pairs on nitrogen, which repel the bonding pairs. The bond angle is slightly less than the tetrahedral angle, approximately 104.5 degrees.

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Key Concepts

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

Lewis Structure

A Lewis structure is a diagram that represents the valence electrons of atoms within a molecule. It shows how electrons are shared between atoms to form covalent bonds and indicates lone pairs. For NH2-, the nitrogen atom is central, bonded to two hydrogen atoms, with a lone pair and an extra electron to account for the negative charge.
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Orbital Overlap

Orbital overlap refers to the interaction between atomic orbitals that leads to bond formation. In NH2-, the nitrogen atom uses sp3 hybrid orbitals to overlap with the 1s orbitals of hydrogen atoms, forming sigma bonds. Understanding orbital overlap helps in visualizing how atoms connect in a molecule.
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Bond Angles

Bond angles are the angles between adjacent bonds around a central atom. They are influenced by the hybridization and the presence of lone pairs. In NH2-, the bond angle is slightly less than the tetrahedral angle of 109.5° due to the repulsion caused by the lone pair on nitrogen, typically around 104.5°.
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Related Practice
Textbook Question

For each of the following compounds and ions,

1. Draw a Lewis structure.

2. Show the kinds of orbitals that overlap to form each bond.

3. Give approximate bond angles around each atom except hydrogen.

d. CH3–CH=CH2

e. HC≡C–CHO

f. H2N–CH2–CN

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Textbook Question

Cyclopropane (C3H6, a three-membered ring) is more reactive than most other cycloalkanes.

c. Suggest why cyclopropane is so reactive.

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Textbook Question

Cyclopropane (C3H6, a three-membered ring) is more reactive than most other cycloalkanes.

a. Draw a Lewis structure for cyclopropane.

b. Compare the bond angles of the carbon atoms in cyclopropane with those in an acyclic (noncyclic) alkane.

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Textbook Question

For each of the following compounds and ions,

1. Draw a Lewis structure.

2. Show the kinds of orbitals that overlap to form each bond.

3. Give approximate bond angles around each atom except hydrogen.

b. [CH2OH]+

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Textbook Question

For each of the following compounds and ions,

1. Draw a Lewis structure.

2. Show the kinds of orbitals that overlap to form each bond.

3. Give approximate bond angles around each atom except hydrogen.

c. CH2=N–CH3

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Textbook Question

If the carbon atom in CH2Cl2 were flat, there would be two stereoisomers. The carbon atom in CH2Cl2 is actually tetrahedral. Make a model of this compound, and determine whether there are any stereoisomers of CH2Cl2. 

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