To draw the Lewis dot structure for carbonic acid (H₂CO₃), follow these steps:
- Count the total number of valence electrons:
- Carbon (C) has 4 valence electrons.
- Each hydrogen (H) has 1 valence electron, and there are 2 hydrogens, so 2 × 1 = 2 electrons.
- Each oxygen (O) has 6 valence electrons, and there are 3 oxygens, so 3 × 6 = 18 electrons.
- Total valence electrons = 4 (C) + 2 (H) + 18 (O) = 24 electrons.
- Determine the central atom: Carbon (C) is the central atom because it is less electronegative than oxygen.
- Draw the skeletal structure: Place the carbon atom in the center and connect it to the two hydrogen atoms and the three oxygen atoms.
- Distribute the remaining electrons:
- First, complete the octet for the outer atoms (hydrogens and oxygens).
- Hydrogen atoms will have 2 electrons each (a single bond).
- Oxygen atoms will have 8 electrons each, including lone pairs.
- After assigning electrons to the outer atoms, place any remaining electrons on the central carbon atom.
- Check the octet rule: Ensure that all atoms (except hydrogen) have 8 electrons around them. If not, form double bonds as needed.
The final Lewis structure for carbonic acid (H₂CO₃) will have:
- Carbon (C) at the center with single bonds to two hydrogen (H) atoms and single bonds to two oxygen (O) atoms.
- One oxygen atom will have a double bond with carbon and two lone pairs.
- The other two oxygen atoms will have single bonds with carbon and three lone pairs each.
Here is the Lewis dot structure for carbonic acid (H₂CO₃):
O || H - C - O - H | O
Remember to include all lone pairs on the oxygen atoms.