Table of contents

1. A Review of General Chemistry5h 5m
2. Molecular Representations1h 14m
3. Acids and Bases2h 46m
4. Alkanes and Cycloalkanes4h 17m
5. Chirality3h 39m
6. Thermodynamics and Kinetics1h 22m
7. Substitution Reactions1h 48m
8. Elimination Reactions2h 30m
9. Alkenes and Alkynes2h 9m
10. Addition Reactions3h 19m
11. Radical Reactions1h 58m
12. Alcohols, Ethers, Epoxides and Thiols2h 42m
13. Alcohols and Carbonyl Compounds2h 17m
14. Synthetic Techniques1h 26m
15. Analytical Techniques:IR, NMR, Mass Spect7h 3m
16. Conjugated Systems6h 13m
17. Ultraviolet Spectroscopy51m
18. Aromaticity2h 34m
19. Reactions of Aromatics: EAS and Beyond5h 1m
20. Phenols55m
21. Aldehydes and Ketones: Nucleophilic Addition4h 56m
22. Carboxylic Acid Derivatives: NAS2h 51m
23. The Chemistry of Thioesters, Phophate Ester and Phosphate Anhydrides1h 10m
24. Enolate Chemistry: Reactions at the Alpha-Carbon1h 53m
25. Condensation Chemistry2h 9m
26. Amines1h 43m
27. Heterocycles2h 0m
28. Carbohydrates5h 53m
29. Amino Acids4h 20m
30. Peptides and Proteins2h 42m
31. Catalysis in Organic Reactions1h 30m
32. Lipids 2h 50m
33. The Organic Chemistry of Metabolic Pathways2h 52m
34. Nucleic Acids1h 32m
35. Transition Metals6h 14m
36. Synthetic Polymers1h 49m

1. A Review of General Chemistry

Molecular Geometry

Organic Chemistry

1. A Review of General Chemistry

Molecular Geometry

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5:27 minutes

Problem 52a

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.
a. [NH₂]^–

Verified step by step guidance

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.

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.

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

Describe the orbitals used in bonding and the bond angles in the following compounds:

d. N₂

Textbook Question

Predict the approximate bond angles for

c. the H—C—N bond angle in (CH₃)₂NH.

d. the H—C—O bond angle in CH₃OCH₃

Textbook Question

Predict the approximate bond angles:

c. the C—N—H bond angle in (CH₃)₂NH

d. the C—N—C bond angle in (CH₃)₂NH

Textbook Question

Use your molecular models to make ethane, and compare the model with the preceding structures.

Textbook Question

For each of the given species:

a. Draw its Lewis structure.

b. Describe the orbitals used by each carbon atom in bonding and indicate the approximate bond angles.

3. CCl₄

Textbook Question

Predict the hybridization of the oxygen atom in water, H₂O. Draw a picture of its three-dimensional structure, and explain why its bond angle is 104.5°.

Multiple Choice

Determine the hybridizationof the following selected atoms:

Multiple Choice

PRACTICE:Determine the hybridization and molecular geometry of the following selected atoms:

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