The molecular-orbital diagrams for two- and four-atom linear chains of lithium atoms are shown in Figure 12.22. Construct a molecular-orbital diagram for a chain containing six lithium atoms and use it to answer the following questions: (a) How many molecular orbitals are there in the diagram?

Key Concepts

Molecular Orbitals

Molecular orbitals (MOs) are formed by the linear combination of atomic orbitals (LCAO) when atoms bond together. In a molecular orbital diagram, these orbitals are depicted based on their energy levels and the number of atomic orbitals involved. For a chain of lithium atoms, the number of MOs corresponds to the total number of atomic orbitals contributed by the atoms in the chain.

Atomic Orbitals in Lithium

Lithium (Li) has an electron configuration of 1s² 2s¹, meaning it has two electrons in the 1s orbital and one in the 2s orbital. In a linear chain of lithium atoms, each atom contributes its 1s and 2s atomic orbitals to the molecular orbital formation. Understanding how these atomic orbitals combine is crucial for determining the total number of molecular orbitals in the chain.

Counting Molecular Orbitals

The total number of molecular orbitals in a system is equal to the number of atomic orbitals that combine to form them. For a chain of six lithium atoms, each contributing two atomic orbitals (1s and 2s), the total number of molecular orbitals can be calculated as 6 atoms × 2 orbitals = 12 molecular orbitals. This principle is fundamental in constructing and analyzing molecular orbital diagrams.