What is the approximate bond angle in the carbonate ion, CO_3^{2-}?

• A. 180^ext{o}
• B. 120^ext{o}
• C. 109.5^ext{o}
• D. 90^ext{o}

Answer: (B)

Verified step by step guidance

1. Identify the central atom in the carbonate ion, CO_3^{2-}, which is carbon (C).
2. Determine the number of regions of electron density around the central atom. In CO_3^{2-}, carbon is bonded to three oxygen atoms and has no lone pairs, so there are three regions of electron density.
3. Use the VSEPR (Valence Shell Electron Pair Repulsion) theory to predict the molecular geometry. Three regions of electron density around the central atom arrange themselves in a trigonal planar shape to minimize repulsion.
4. Recall that in a trigonal planar geometry, the bond angles between the atoms are approximately 120^{\circ}.
5. Conclude that the approximate bond angle in the carbonate ion, CO_3^{2-}, is 120^{\circ}.