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Ch.9 - Chemical Bonding I: The Lewis Model
All textbooksTro 4th EditionCh.9 - Chemical Bonding I: The Lewis ModelProblem 76
Chapter 9, Problem 76

Write Lewis structures for each molecule or ion. Include resonance structures if necessary and assign formal charges to all atoms. If you need to, expand the octet on the central atom to lower formal charge. a. SO4^2- b. HSO4^- c. SO3 d. BrO2^-

Verified step by step guidance
1
Step 1: Determine the total number of valence electrons for each molecule or ion. For ions, adjust the count by adding or subtracting electrons based on the charge.
Step 2: Identify the central atom (usually the least electronegative element) and arrange the other atoms around it. Connect each surrounding atom to the central atom with a single bond.
Step 3: Distribute the remaining valence electrons as lone pairs to satisfy the octet rule for each atom, starting with the most electronegative atoms. If necessary, expand the octet on the central atom to accommodate extra electrons.
Step 4: Check for resonance structures by moving electrons to form double or triple bonds where possible, ensuring that the formal charges are minimized across the structure.
Step 5: Calculate the formal charge for each atom using the formula: \( \text{Formal Charge} = \text{Valence Electrons} - \text{Non-bonding Electrons} - \frac{1}{2} \times \text{Bonding Electrons} \). Adjust the structure to minimize formal charges, expanding the octet if necessary.

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 use dots to represent valence electrons and lines to represent bonds. Understanding how to draw these structures is essential for visualizing molecular geometry and predicting reactivity.
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Resonance Structures

Resonance structures are different ways of drawing the same molecule that show the delocalization of electrons. They are used when a single Lewis structure cannot adequately represent the electron distribution. The actual structure is a hybrid of these resonance forms, which helps in understanding the stability and reactivity of the molecule.
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Formal Charge

Formal charge is a theoretical charge assigned to an atom in a molecule, calculated based on the number of valence electrons, the number of bonds, and the number of lone electrons. It helps in determining the most stable Lewis structure, as structures with lower formal charges on atoms are generally more favorable. Assigning formal charges is crucial for evaluating resonance structures and octet expansion.
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Related Practice
Textbook Question

Write the Lewis structure for each molecule (octet rule not followed). b. NO2

Textbook Question

Write the Lewis structure for each molecule (octet rule not followed). a. BBr3 b. NO c. ClO2

Textbook Question

Write Lewis structures for each molecule or ion. Use expanded octets as necessary. a. PF5

Textbook Question

Write Lewis structures for each molecule or ion. Use expanded octets as necessary. b. AsF6-

Textbook Question

Order these compounds in order of increasing carbon–carbon bond strength: HCCH, H2CCH2, H3CCH3.