Related Problems with Solutions
Problem 3 : Explain the concept of resonance in the carbonate ion (CO₃²⁻). Draw resonance structures and calculate the formal charges on carbon and oxygen atoms.
Solution :
The carbonate ion (CO₃²⁻) exhibits resonance. Here are its resonance structures:
Structure 1:
O
/
C O⁻
Structure 2: O⁻ | C | O
Structure 3:
O⁻
/
C O
To calculate formal charges:
- Carbon (C) has 4 valence electrons.
- Oxygen (O) has 6 valence electrons.
For each structure, calculate the formal charges:
-
Structure 1: FC(C) = 4 - 3 - 0 = +1 FC(O, top) = 6 - 2 - 1 = +3 FC(O, bottom) = 6 - 1 - 1 = +4
-
Structure 2: FC(C) = 4 - 2 - 1 = +1 FC(O) = 6 - 3 - 0 = +3
-
Structure 3: FC(C) = 4 - 3 - 1 = 0 FC(O, left) = 6 - 2 - 0 = +4 FC(O, right) = 6 - 1 - 0 = +5
The actual ion is a resonance hybrid of these structures.
