To determine the correct Lewis structure for formaldehyde (CH₂O), we need to follow these steps:
1. Count the total number of valence electrons:
- Carbon (C) has 4 valence electrons.
- Hydrogen (H) has 1 valence electron each (there are 2 hydrogens, so 2 electrons in total).
- Oxygen (O) has 6 valence electrons.
Total valence electrons: 4 (C) + 2 × 1 (H) + 6 (O) = 12 valence electrons.
2. Determine the central atom:
- Carbon (C) is generally the central atom as it can form more bonds compared to Hydrogen. Oxygen (O) often forms two bonds.
3. Draw a skeleton structure:
- Connect C to H, and C to O with single bonds initially.
- [tex]\[ H - C - O - H \][/tex]
4. Distribute the remaining electrons:
- We've used 4 electrons to form the three single bonds (C-H, C-H, and C-O).
- Total valence electrons used: 4.
Remaining valence electrons: 12 - 4 = 8.
- Place remaining electrons around Oxygen to satisfy the octet rule:
- Oxygen needs 8 electrons (duet rule using pairs). We already have 2 shared electrons forming one single bond with carbon.
- Place 6 more electrons (3 pairs) around Oxygen (total 8 with shared ones).
5. Form double bonds if necessary:
- Carbon needs 8 electrons around it as well. Right now, carbon is sharing 4 electrons (2 from each H-C bond and 2 from the C-O bond).
- There are 2 available electrons on oxygen that can be shared to make a double bond.
Putting it all together, we get:
H
|
H—C = O
|
In this structure:
- Each Hydrogen has 2 electrons (satisfied).
- Carbon has 8 electrons.
- Oxygen has 8 electrons.
The correct Lewis structure is:
H
|
H—C=O
|
Therefore, the correct answer is C.
Explanation:
- The correct Lewis structure has each Hydrogen atom single bonded to the Carbon atom.
- The Oxygen is double-bonded to the Carbon atom, sharing two pairs of electrons.
