What is the hybridization of carbon in CO32−?
The Correct Answer and Explanation is:
The hybridization of carbon in the carbonate ion (CO₃²⁻) is sp².
Explanation:
In the carbonate ion, CO₃²⁻, there are three oxygen atoms bonded to a central carbon atom. The ion has a trigonal planar geometry, meaning that all atoms in the ion lie in a single plane and the bond angles between the oxygen atoms are approximately 120°. This geometry suggests the involvement of sp² hybridization of the central carbon atom.
Step-by-Step Breakdown:
- Electron Configuration: Carbon has an atomic number of 6, which gives it an electron configuration of 1s² 2s² 2p². In the carbonate ion, carbon forms three bonds, one with each of the three oxygen atoms.
- Bonding in CO₃²⁻: The carbonate ion has a resonance structure, meaning the double bond is not fixed between a single oxygen and the carbon, but is delocalized over the three oxygen atoms. The actual bonding in CO₃²⁻ is an average of three equivalent bonds, all of which are partial (each bond being about one and a third of a full bond).
- Electron Domain Count: Carbon forms three sigma bonds with the oxygen atoms. There are no lone pairs on the carbon atom, and the delocalization of electrons suggests that the carbon atom is involved in three equivalent bonds with the oxygens. The ion as a whole carries a 2− charge, which is delocalized over the three oxygens.
- sp² Hybridization: In sp² hybridization, the central atom uses one s orbital and two p orbitals to form three equivalent sp² hybrid orbitals, which then form sigma bonds with the three oxygens. The unhybridized p orbital remains available for the delocalized pi-bonding that occurs in the resonance structure, contributing to the overall bonding in CO₃²⁻.
- Geometry: The geometry around the central carbon atom is trigonal planar, which is consistent with sp² hybridization, where the three hybrid orbitals are arranged at 120° angles.
In conclusion, the carbon in CO₃²⁻ is sp² hybridized, as evidenced by its trigonal planar geometry, delocalized electron bonding, and the absence of lone pairs on the carbon atom.