Calcium carbide, CaC2, reacts with water to produce acetylene,C2H2, and is sometimes used as a convenient source ofthat substance. Use the MO energy diagram in Figure 8.22ato describe the bonding in the carbide anion, C22-. What isits bond order?

Verified step by step guidance

1. Step 1: The carbide anion, C22-, is a diatomic molecule. In order to understand its bonding, we need to fill in the molecular orbital (MO) energy diagram. The MO energy diagram for a diatomic molecule like C22- consists of a series of energy levels representing bonding and antibonding molecular orbitals. The energy levels are filled with electrons starting from the lowest energy level.
2. Step 2: Each carbon atom has 6 electrons, so the C22- anion, which has two extra electrons, has a total of 14 electrons. Start filling in the MO energy diagram from the lowest energy level, which is the sigma 1s orbital, and continue to the higher energy levels. Each orbital can hold a maximum of 2 electrons.
3. Step 3: After filling in the sigma 1s, sigma* 1s, sigma 2s, and sigma* 2s orbitals, you will have 8 electrons left. These will fill the pi 2p and sigma 2p orbitals. The pi 2p orbitals can hold 4 electrons and the sigma 2p orbital can hold 2 electrons.
4. Step 4: To calculate the bond order, use the formula: Bond Order = 0.5 * (Number of electrons in bonding orbitals - Number of electrons in antibonding orbitals). In this case, the bonding orbitals are sigma 1s, sigma 2s, pi 2p, and sigma 2p, and the antibonding orbitals are sigma* 1s and sigma* 2s.
5. Step 5: Plug the number of electrons in the bonding and antibonding orbitals into the bond order formula to calculate the bond order of the C22- anion. A higher bond order indicates a stronger, more stable bond.

Key Concepts

Molecular Orbital Theory

Molecular Orbital (MO) Theory explains how atomic orbitals combine to form molecular orbitals, which can be occupied by electrons. In this theory, bonding and antibonding orbitals are formed, and the distribution of electrons in these orbitals determines the stability and properties of the molecule. Understanding MO diagrams is crucial for analyzing the bonding characteristics of complex ions like the carbide anion.

Bond Order

Bond order is a measure of the number of chemical bonds between a pair of atoms, calculated as the difference between the number of bonding and antibonding electrons divided by two. It provides insight into the strength and stability of a bond; a higher bond order indicates a stronger bond. In the case of the carbide anion, determining the bond order helps assess the nature of the bonding between carbon atoms.

Carbide Anion Structure

The carbide anion, C2^2-, consists of two carbon atoms sharing electrons, resulting in a unique bonding arrangement. This anion can be analyzed using MO theory to understand its electronic configuration and stability. The structure and bonding characteristics of the carbide anion are essential for predicting its reactivity and the products formed during its reactions, such as with water.