Write the molecular orbital configuration of Be2. Calculate its bond order and predict its magnetic behavior and stability.
The Correct Answer and Explanation is:
Molecular Orbital Configuration of Be₂
Beryllium (Be) has an atomic number of 4, and its electron configuration is ( 1s^2 2s^2 ). When two beryllium atoms combine to form the diatomic molecule Be₂, the molecular orbital theory is used to determine the molecular orbital configuration.
The molecular orbitals for Be₂ can be represented as follows:
- Bonding Molecular Orbitals:
- ( \sigma_{1s} ): Filled with 2 electrons from the 1s orbitals of each Be atom.
- ( \sigma_{2s} ): Filled with 2 electrons from the 2s orbitals of each Be atom.
- Antibonding Molecular Orbitals:
- ( \sigma^*_{2s} ): Unoccupied (0 electrons).
Thus, the molecular orbital configuration for Be₂ is:
[
\text{Be}2: ( \sigma{1s} )^2 ( \sigma_{2s} )^2 ( \sigma^*_{2s} )^0
]
Bond Order Calculation
The bond order can be calculated using the formula:
[
\text{Bond Order} = \frac{(\text{Number of electrons in bonding MOs}) – (\text{Number of electrons in antibonding MOs})}{2}
]
For Be₂:
- Electrons in bonding MOs: ( 2 (\sigma_{1s}) + 2 (\sigma_{2s}) = 4 )
- Electrons in antibonding MOs: ( 0 (\sigma^*_{2s}) = 0 )
Therefore, the bond order is:
[
\text{Bond Order} = \frac{4 – 0}{2} = 2
]
Magnetic Behavior and Stability
- Magnetic Behavior: Be₂ has no unpaired electrons in its molecular orbitals, making it diamagnetic. This means that it will not be attracted to a magnetic field.
- Stability: The bond order of 2 indicates that Be₂ has a strong double bond, suggesting that the molecule is stable. However, due to the relatively small size of beryllium and the resulting weak overlapping of the ( s ) orbitals, Be₂ is not a very stable molecule under normal conditions. In fact, it is considered less stable than other diatomic molecules like O₂ or N₂.
In summary, the molecular orbital configuration of Be₂ reveals a bond order of 2, indicating a stable diatomic molecule that is diamagnetic due to the absence of unpaired electrons.