Chapter 4 - Review Questions - Page 197: 8

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To show how 2s orbitals combine to form σ bonding and σ antibonding molecular orbitals, and how 2p orbitals overlap to form σ bonding, π bonding, π antibonding, and σ antibonding molecular orbitals, we can use the principles of molecular orbital theory. 1. Combination of 2s orbitals: - When two 2s orbitals overlap, they can form two molecular orbitals: a σ bonding orbital and a σ antibonding orbital. - The σ bonding orbital is formed by the constructive interference of the two 2s orbitals, resulting in a higher electron density between the nuclei. This increases the stability of the molecule and is a bonding interaction. - The σ antibonding orbital is formed by the destructive interference of the two 2s orbitals, resulting in a lower electron density between the nuclei. This decreases the stability of the molecule and is an antibonding interaction. 2. Combination of 2p orbitals: - When two 2p orbitals overlap, they can form four molecular orbitals: a σ bonding orbital, a π bonding orbital, a π antibonding orbital, and a σ antibonding orbital. - The σ bonding orbital is formed by the head-to-head overlap of the 2p orbitals, resulting in a higher electron density between the nuclei. This is a bonding interaction. - The π bonding orbitals are formed by the side-by-side overlap of the 2p orbitals, resulting in a higher electron density above and below the internuclear axis. This is also a bonding interaction. - The π antibonding orbitals are formed by the destructive interference of the side-by-side 2p orbitals, resulting in a lower electron density above and below the internuclear axis. This is an antibonding interaction. - The σ antibonding orbital is formed by the destructive interference of the head-to-head 2p orbitals, resulting in a lower electron density between the nuclei. This is an antibonding interaction. The combination of 2s and 2p orbitals to form these molecular orbitals is crucial in understanding the stability and reactivity of molecules, as the occupation of these orbitals by electrons determines the overall bonding and antibonding interactions within the molecule.