a. Drawing the Lewis Structure:
To draw the Lewis structure of the carbonate ion (CO3^2-), we start by counting the total number of valence electrons. Carbon (C) has 4 valence electrons, and each oxygen (O) has 6, giving us a total of 24 valence electrons for three oxygens. Since the ion has a -2 charge, we add 2 more electrons, resulting in a total of 26 valence electrons. Next, we place carbon in the center and arrange the three oxygen atoms around it. We connect the carbon to each oxygen with a single bond initially and distribute the remaining electrons to satisfy the octet rule for oxygen atoms, resulting in one of the oxygens being double-bonded to carbon. This gives the final structure with resonance forms where the double bond can be between carbon and any of the three oxygen atoms.
b. Hybrid Orbitals:
In the carbonate ion, the central carbon atom undergoes sp2 hybridization. This hybridization occurs because carbon forms three equivalent sp2 hybrid orbitals to form three sigma bonds with the oxygen atoms.
c. O-C-O Angle:
The O-C-O bond angle in the carbonate ion is approximately 120 degrees. This angle is characteristic of trigonal planar geometry, which is a result of the sp2 hybridization of the central carbon atom.
d. Sigma and Pi Bonds:
In the CO3^2- ion, there are a total of three sigma bonds (one from carbon to each oxygen) and two pi bonds (one pi bond for the double bond between carbon and one of the oxygen atoms). This results from the resonance structures, where the double bond is delocalized among the three oxygen atoms.