You drew the Lewis structures of the following compounds and ion in Assessment 2.32. Predict their shapes around the central atom based on the Lewis structure.
(d) CO₃^2-

Verified step by step guidance

1. Draw the Lewis structure for the carbonate ion (CO₂⁻/₃). Start by determining the total number of valence electrons. Carbon has 4 valence electrons, each oxygen has 6 valence electrons, and the ion has a -2 charge, adding 2 more electrons. This gives a total of 24 valence electrons.
2. Distribute the electrons around the central carbon atom and the three oxygen atoms. Place carbon in the center and connect it to each oxygen atom with a single bond. Then, distribute the remaining electrons to satisfy the octet rule for each oxygen atom.
3. Check the formal charges on each atom. Adjust the structure by forming double bonds between carbon and one or more oxygen atoms to minimize formal charges, ensuring the most stable resonance structures. The carbonate ion has three resonance structures where the double bond is delocalized among the three oxygen atoms.
4. Determine the electron geometry using the VSEPR (Valence Shell Electron Pair Repulsion) theory. The central carbon atom is surrounded by three regions of electron density (three oxygen atoms), which corresponds to a trigonal planar electron geometry.
5. Predict the molecular shape. Since there are no lone pairs on the central carbon atom, the molecular shape of the carbonate ion is also trigonal planar, with bond angles of approximately 120°.

Key Concepts

Lewis Structures

Lewis structures are diagrams that represent the bonding between atoms in a molecule and the lone pairs of electrons that may exist. They help visualize the arrangement of electrons and the connectivity of atoms, which is crucial for predicting molecular geometry. In the case of CO₂⁻/₃, understanding its Lewis structure will provide insight into the distribution of electrons and the overall shape of the molecule.

VSEPR Theory

Valence Shell Electron Pair Repulsion (VSEPR) theory is a model used to predict the geometry of individual molecules based on the repulsion between electron pairs in the valence shell of the central atom. According to VSEPR, electron pairs will arrange themselves to minimize repulsion, leading to specific molecular shapes. This theory is essential for determining the three-dimensional arrangement of atoms in CO₂⁻/₃.

Molecular Geometry

Molecular geometry refers to the three-dimensional arrangement of atoms within a molecule. It is influenced by the number of bonding pairs and lone pairs of electrons around the central atom, as predicted by Lewis structures and VSEPR theory. Understanding the molecular geometry of CO₂⁻/₃ is vital for predicting its physical and chemical properties, as well as its reactivity.