The Lewis structure of the CO32- ion is __.
The correct answer and explanation is:
The Lewis structure of the carbonate ion (CO₃²⁻) is a trigonal planar structure with a central carbon atom bonded to three oxygen atoms. Each oxygen atom forms a single bond with the carbon, and there are resonance structures in which one of the oxygen atoms has a double bond to the carbon while the other two have single bonds with a negative charge.
To explain this, the total number of valence electrons in the CO₃²⁻ ion is the key starting point. Carbon has 4 valence electrons, and each oxygen atom has 6 valence electrons, giving a total of 18 electrons from the atoms themselves. However, since the ion carries a 2- charge, two additional electrons are added, making the total number of electrons 24.
In the basic structure, the carbon atom is placed in the center with three oxygen atoms around it. The electrons are first placed to form single bonds between carbon and oxygen. Each single bond uses 2 electrons. After placing these 6 electrons (3 bonds), 18 electrons remain.
The remaining electrons are placed as lone pairs on the oxygen atoms. Since the ion is negatively charged, one of the oxygen atoms must have a double bond with carbon to minimize the charge separation. The other two oxygen atoms will have single bonds with carbon and each will carry a negative charge.
This structure is a resonance hybrid, meaning that the actual structure is a blend of the three possible resonance structures, where the double bond can be placed between carbon and any of the three oxygen atoms. The bond order for each C-O bond in the CO₃²⁻ ion is 1⅓, indicating that the bonds are somewhere between single and double in nature.
The geometry of the CO₃²⁻ ion is trigonal planar because all three bonding pairs of electrons are arranged symmetrically around the carbon atom, creating an angle of 120° between them. This results in a stable configuration with delocalized electrons, explaining the ion’s stability.