Multiple Choice
Which of the following correctly describes the molecular orbital energy diagram for the diatomic molecule H_2?
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12. Molecular Shapes & Valence Bond Theory
Molecular Orbital Theory
Multiple Choice
Which of the following correctly represents the molecular orbital energy diagram for the diatomic molecule Li_2?
A
The diagram shows two electrons occupying the sigma_{2s} bonding orbital, with no electrons in the sigma_{2s}^* antibonding orbital.
B
The diagram shows one electron in the sigma_{1s} bonding orbital and one electron in the sigma_{1s}^* antibonding orbital.
C
The diagram shows both electrons occupying the sigma_{2s}^* antibonding orbital.
D
The diagram shows one electron in the sigma_{2s} bonding orbital and one electron in the sigma_{2s}^* antibonding orbital.
Verified step by step guidance1
Identify the total number of valence electrons in the Li_2 molecule. Each lithium atom has 3 electrons, with 1 valence electron in the 2s orbital, so Li_2 has 2 valence electrons in total.
Recall the order of molecular orbitals for homonuclear diatomic molecules of period 2 elements like Li_2, focusing on the 2s orbitals: the bonding orbital is \$\(\sigma\)_{2s}\$ and the antibonding orbital is \$\(\sigma\)_{2s}^*\$.
Place the 2 valence electrons into the molecular orbitals starting from the lowest energy level, which is the bonding \$\(\sigma\)_{2s}\$ orbital, following the Pauli exclusion principle and Hund's rule.
Since there are only 2 electrons, both will occupy the \$\(\sigma\)_{2s}\$ bonding orbital, and the \$\(\sigma\)_{2s}^*\$ antibonding orbital remains empty.
Conclude that the correct molecular orbital diagram for Li_2 shows two electrons in the \$\(\sigma\)_{2s}\$ bonding orbital and none in the \$\(\sigma\)_{2s}^*\$ antibonding orbital.
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