Assign formal charges to the atoms in the following structures. Which of the two do you think is the more important contributor to the resonance hybrid?(a)(b)

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Step 1: Understand the concept of formal charge. Formal charge is a bookkeeping tool used in chemistry to help determine the most likely structure of a molecule. It is calculated using the formula: Formal Charge = (Valence electrons) - (Non-bonding electrons) - (Bonding electrons/2).

Step 2: Identify the valence electrons for each atom in the given structures. Use the periodic table to find the number of valence electrons for each atom involved in the structures.

Step 3: Count the non-bonding electrons (lone pairs) and bonding electrons (shared in bonds) for each atom in the structures.

Step 4: Calculate the formal charge for each atom in both structures using the formula from Step 1.

Step 5: Compare the formal charges and overall stability of the two structures. The structure with formal charges closest to zero and/or the most electronegative atoms bearing negative charges is generally the more important contributor to the resonance hybrid.

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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 Lewis structure by minimizing the formal charges across the molecule.

Resonance Structures

Resonance structures are different Lewis structures for the same molecule that depict the delocalization of electrons. These structures are not real, but rather a way to represent the hybrid of all possible configurations, which contributes to the overall stability and reactivity of the molecule.

Resonance Hybrid

The resonance hybrid is the actual structure of a molecule that is a weighted average of all its resonance structures. It reflects the delocalization of electrons and is often more stable than any individual resonance structure, as it accounts for the contributions of all possible configurations.

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