Draw the Lewis structure for the carbonate ion, CO32 on your shown work. (The carbon atom is the central atom)
How many total valence electrons did you use in your structure?
12
20
24
22
The Correct Answer and Explanation is :
The carbonate ion (CO₃²⁻) consists of one carbon atom (C) bonded to three oxygen atoms (O). In this structure, the carbon atom is the central atom, and it is bonded to the three oxygen atoms in a trigonal planar geometry. The carbonate ion has a -2 charge, which is distributed across the three oxygen atoms.
Steps to Draw the Lewis Structure:
- Valence Electrons: Carbon (C) is in group 14 of the periodic table and has 4 valence electrons. Each oxygen (O) atom is in group 16, contributing 6 valence electrons. Since there are three oxygen atoms, the total valence electrons from oxygen are 6 × 3 = 18. The carbonate ion has a -2 charge, so we add 2 more electrons. Therefore, the total number of valence electrons is 4 (from carbon) + 18 (from oxygen) + 2 (from the charge) = 24 valence electrons.
- Bonding: Carbon forms single bonds with each oxygen atom. Since carbon has only 4 valence electrons, we need to make use of double bonds to satisfy the octet rule. This results in two oxygen atoms forming double bonds with the carbon atom.
- Electron Distribution: After bonding, there are still extra electrons. These are placed as lone pairs on the oxygen atoms. The formal charges on the oxygen atoms are adjusted to ensure that the sum of all formal charges is -2, which matches the charge of the ion.
Total Valence Electrons:
The correct number of valence electrons used in the structure is 24, as calculated from the sum of the valence electrons from carbon, oxygen, and the extra electrons from the negative charge.