The molecular orbital theory diagram for Li2 illustrates the arrangement of molecular orbitals formed from the atomic orbitals of the two lithium atoms. In the case of Li2, the 1s orbitals of each lithium combine to form two molecular orbitals: a bonding sigma (σ) orbital and an antibonding sigma star (σ*) orbital.
The molecular orbital filling for Li2 follows Hund’s Rule and the Pauli Exclusion Principle. Each lithium atom has an atomic number of 3, meaning that each contributes three electrons, but only the first two electrons fill the bonding molecular orbital while the third will occupy the antibonding orbital.
The bond order can be calculated using the formula:
Bond Order = (Number of bonding electrons – Number of antibonding electrons) / 2
For Li2, we have:
- Bonding electrons = 2 (from the σ orbital)
- Antibonding electrons = 1 (from the σ* orbital)
Thus, the bond order calculation will be:
Bond Order = (2 – 1) / 2 = 0.5
Since Li2 has unpaired electrons in its antibonding orbital, it is considered paramagnetic. This means it is attracted to magnetic fields due to the presence of these unpaired electrons.