Formal Charge Problems (9)

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Introduction

This video explains how to calculate the formal charge of each atom in a given molecule and determine the overall charge of the molecule. It walks through each step, highlighting the number of bonding and non-bonding electrons involved.

Main Points/Arguments

Formal Charge Calculation:

- Formula: Formal Charge = (Valence electrons in neutral atom) - (1/2 number of bonding electrons) - (Number of non-bonding electrons)

- This formula helps assign the charge to specific atoms within a molecule.

Hydrogen Atoms:

- Bonding Electrons: 2 (one bond with carbon).

- Non-Bonding Electrons: 0.

- Calculation: 1 (valence electron) - (1/2 * 2) - 0 = 0.

- Conclusion: Each hydrogen atom has a formal charge of 0.

- Rule of Thumb: Hydrogens with one bond generally have a formal charge of 0.

Carbon Atoms:

- First Carbon Atom:

    - **Bonding Electrons:** 8 (four bonds).
    - **Non-Bonding Electrons:** 0.
    - **Calculation:** 4 (valence electrons) - (1/2 * 8) - 0 = 0.
    - **Conclusion:** This carbon has a formal charge of 0.

- Second Carbon Atom:

    - **Bonding Electrons:** 8 (four bonds).
    - **Non-Bonding Electrons:** 0.
    - **Calculation:** 4 (valence electrons) - (1/2 * 8) - 0 = 0.
    - **Conclusion:** This carbon is neutral with a formal charge of 0.

Nitrogen Atom:

- Bonding Electrons: 8 (four bonds).

- Non-Bonding Electrons: 0.

- Calculation: 5 (valence electrons) - (1/2 * 8) - 0 = +1.

- Conclusion: This nitrogen has a formal charge of +1.

Oxygen Atom:

- Bonding Electrons: 2 (one bond).

- Non-Bonding Electrons: 6 (three lone pairs).

- Calculation: 6 (valence electrons) - (1/2 * 2) - 6 = -1.

- Conclusion: This oxygen has a formal charge of -1.

Examples or Evidence

Overall Charge:

- Adding the formal charges: +1 (nitrogen) + -1 (oxygen) = 0.

- The molecule is overall neutral but contains atoms with formal charges.

Additional Insights or Context

Molecule Example:

- The molecule discussed is acetone oxime.

- Understanding the distribution of formal charges helps in analyzing molecular structure and reactivity.

Conclusion

The video demonstrates the application of the formal charge formula to a molecule, highlighting how to calculate and assign charges to specific atoms. The overall charge of the molecule is determined by summing the formal charges of individual atoms, showing that the molecule is neutral overall.

Formal Charge Problems (9)