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

Formal Charges

Organic Chemistry

1. A Review of General Chemistry

Formal Charges

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4:41 minutes

Problem 85a

Textbook Question

Looking ahead in Chapter 3, we describe how the formal charge on an atom can be used to predict the number of lone pairs. Given the charge, or lack of charge, on each atom, fill in the electron pairs.
(a)

Verified step by step guidance

Identify the formal charge on each atom in the molecule. Recall that formal charge is calculated using the formula:

Formal Charge = (Valence Electrons) - (Non-Bonding Electrons) - (1/2 × Bonding Electrons)

Determine the number of valence electrons for each atom based on its position in the periodic table. For example, oxygen has 6 valence electrons, nitrogen has 5, etc.

Using the formal charge and the number of valence electrons, calculate the number of lone pair electrons for each atom. Lone pairs are the non-bonding electrons that remain after accounting for bonding electrons.

Draw the Lewis structure of the molecule, ensuring that the total number of electrons matches the sum of the valence electrons for all atoms in the molecule. Place lone pairs on atoms to satisfy their formal charges and the octet rule (if applicable).

Double-check the structure to ensure that the formal charges on all atoms are consistent with the given information and that the total charge of the molecule matches the overall charge (if any).

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Key Concepts

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

Formal Charge

Formal charge is a theoretical charge assigned to an atom in a molecule, calculated by taking the number of valence electrons in the free atom, subtracting the number of non-bonding electrons, and half the number of bonding electrons. It helps in determining the most stable structure of a molecule by minimizing the formal charges across the atoms.

Lone Pairs

Lone pairs are pairs of valence electrons that are not involved in bonding and are localized on a single atom. They play a crucial role in determining the geometry and reactivity of molecules, as they can influence the shape and polarity of the molecule due to their repulsive interactions with bonding pairs.

Electron Pair Geometry

Electron pair geometry refers to the spatial arrangement of all electron pairs (bonding and lone pairs) around a central atom. Understanding this geometry is essential for predicting molecular shapes and angles, which are determined by the repulsion between electron pairs according to VSEPR (Valence Shell Electron Pair Repulsion) theory.

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Related Practice

Textbook Question

Draw the Lewis structure for the following ions. Be sure to calculate the formal charge of each atom to confirm that your structure is correct.

(b) H⁺

Textbook Question

Draw the Lewis structure for the following ions. Be sure to calculate the formal charge of each atom to confirm that your structure is correct.

(d) AlCl₄^-

Textbook Question

Calculate the formal charge of the indicated atoms in the ions shown.

Textbook Question

Calculate the formal charge on the non-hydrogen atoms in the molecules shown. Use the arrow-pushing formalism to 'move' an electron pair such that it is shared between two (formerly) charged atoms. Your arrow should account for the formation of the molecule on the right from the molecule on the left.

Textbook Question

Based on the formal charge, determine how many lone pairs are on each indicated atom.

(a)

Textbook Question

Give each atom the appropriate formal charge:

Textbook Question

Draw the missing lone-pair electrons and assign the missing formal charges for the following:

Textbook Question

Give each atom the appropriate formal charge:

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Looking ahead in Chapter 3, we describe how the formal charge on an atom can be used to predict the number of lone pairs. Given the charge, or lack of charge, on each atom, fill in the electron pairs. (a)

Key Concepts

Formal Charge

Lone Pairs

Electron Pair Geometry

Watch next

Looking ahead in Chapter 3, we describe how the formal charge on an atom can be used to predict the number of lone pairs. Given the charge, or lack of charge, on each atom, fill in the electron pairs.
(a)