To begin with, we need to understand the basic concepts of Atomic Orbitals (AOs) and Molecular Orbitals (MOs) for the lithium dimer, Li2.
In the case of Li2, each lithium atom has the electronic configuration of 1s2 2s1. When two lithium atoms come together to form the diatomic molecule, their atomic orbitals combine to form molecular orbitals.
Atomic Orbital Diagram:
The atomic orbitals involved in the bonding of Li2 are the 1s and 2s orbitals. Each lithium atom contributes one 1s and one 2s orbital.
- 1s: Two electrons from both lithium atoms (1s2).
- 2s: One electron from each lithium atom (2s1).
Molecular Orbital Diagram:
When we combine the atomic orbitals, we get the following molecular orbitals for Li2:
- (σ1s): Bonding molecular orbital formed from the combination of the 1s orbitals.
- (σ1s*): Antibonding molecular orbital corresponding to (σ1s).
- (σ2s): Bonding molecular orbital formed from the combination of the 2s orbitals.
- (σ2s*): Antibonding molecular orbital corresponding to (σ2s).
The configuration of Li2 in terms of molecular orbitals can be described as follows:
Li2 will have a total of 4 electrons where:
- 2 electrons will occupy the bonding σ1s molecular orbital.
- 2 electrons will occupy the bonding σ2s molecular orbital.
Therefore, the molecular orbital configuration for Li2 can be represented as: (σ1s)2 (σ2s)2.
Energy Diagram:
This diagram illustrates the energy levels of both the atomic and molecular orbitals. Note how the bonding orbitals are lower in energy compared to their corresponding antibonding orbitals.
In conclusion, the Li2 molecule is a stable diatomic molecule due to the filling of its bonding molecular orbitals, leading to a net bonding interaction.