Draw a valid Lewis structure for the molecule CH3NO in which there are no nonzero formal charges on any of the atoms. This structure should not include any bonds between N and O.
The Correct Answer and Explanation is:
To draw the Lewis structure for CH₃NO (formaldehyde oxime) where there are no nonzero formal charges on any of the atoms and without a bond between nitrogen and oxygen, follow these steps:
1. Count the total valence electrons:
- Carbon (C): 4 valence electrons (since C is in group 14).
- Hydrogen (H): 1 valence electron each, for 3 H atoms → 3 electrons.
- Nitrogen (N): 5 valence electrons (since N is in group 15).
- Oxygen (O): 6 valence electrons (since O is in group 16).
Total valence electrons = 4 (C) + 3 (H) + 5 (N) + 6 (O) = 18 valence electrons.
2. Determine the skeleton structure:
- Carbon typically forms four bonds, so it will be the central atom.
- Hydrogen atoms will be attached to carbon, as carbon can only form single bonds.
- Nitrogen and oxygen will be attached to carbon, but we will not directly connect nitrogen and oxygen.
3. Place atoms and connect them with single bonds:
- Attach each hydrogen atom to the carbon atom.
- Attach nitrogen and oxygen atoms to the carbon atom via single bonds.
The skeleton structure looks like this:
H—C—N—O
4. Distribute the electrons:
- Each bond represents 2 electrons. For 4 C—H bonds (3 H atoms), we use 8 electrons.
- The C—N and C—O single bonds use 2 more electrons, making 10 electrons used so far.
5. Complete the octets:
- Oxygen needs 2 more electrons to complete its octet. Place these electrons as lone pairs on oxygen.
- Nitrogen needs 2 more electrons to complete its octet. Place these electrons as lone pairs on nitrogen.
Now, there are 18 total electrons used (8 for C—H bonds, 2 for C—N, 2 for C—O, and 6 for lone pairs).
6. Check for formal charges:
- Carbon: The formal charge is calculated by subtracting the number of bonds (4) and lone pairs (0) from the valence electrons (4), resulting in a formal charge of 0.
- Hydrogen: Each hydrogen has 1 bond, which is correct for its 1 valence electron, resulting in no formal charge on hydrogen.
- Nitrogen: Nitrogen has 1 bond to carbon and 2 lone pairs. This gives a formal charge of 0 (5 valence electrons minus 1 bond and 2 lone pairs).
- Oxygen: Oxygen has 1 bond to carbon and 3 lone pairs, giving a formal charge of 0 (6 valence electrons minus 1 bond and 3 lone pairs).
7. Final structure:
mathematicaCopyEditH—C—N—O
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H H
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H
This structure has no formal charges on any atom and follows the given conditions.
