The Lewis structure of carbonate (CO₃²⁻) is a representation of the molecule that shows the arrangement of valence electrons around the atoms. Carbonate is a polyatomic ion with a central carbon atom surrounded by three oxygen atoms.
Here’s how the Lewis structure is determined:
- Count the total number of valence electrons: Carbon has 4 valence electrons, and each oxygen has 6 valence electrons. Since carbonate has a 2- charge, add 2 more electrons. Total valence electrons = 4 + (3 × 6) + 2 = 24.
- Place the least electronegative atom in the center: Carbon is less electronegative than oxygen, so it is placed in the center.
- Connect the atoms with single bonds: Draw single bonds between the carbon and each oxygen atom. This uses 6 electrons (3 bonds × 2 electrons).
- Distribute the remaining electrons: Place the remaining 18 electrons around the oxygen atoms to satisfy the octet rule. Each oxygen should have 8 electrons around it.
- Check for formal charges: The formal charge on carbon is 0, and each oxygen has a formal charge of -1. The overall charge of the ion is 2-, which matches the carbonate ion.
The final Lewis structure shows carbon double-bonded to one oxygen and single-bonded to the other two oxygens, with lone pairs on the oxygens to complete their octets.