li2 is stable but be2 is not stable . explain
The Correct Answer and Explanation is :
The stability of diatomic molecules like Li₂ and Be₂ can be explained using molecular orbital (MO) theory, which describes how atomic orbitals combine to form molecular orbitals.
Lithium (Li₂):
Each lithium atom has an electronic configuration of 1s² 2s¹. When two lithium atoms bond to form Li₂, their atomic orbitals combine to form molecular orbitals. The bonding molecular orbitals (σ1s and σ2s) are filled with electrons, while the antibonding molecular orbitals (σ1s and σ2s) remain empty. This results in a bond order of 1, indicating a stable bond between the two lithium atoms. Additionally, all electrons in Li₂ are paired, making it a diamagnetic molecule.
Beryllium (Be₂):
Each beryllium atom has an electronic configuration of 1s² 2s². In the Be₂ molecule, the bonding molecular orbitals (σ1s and σ2s) are filled with electrons, and the antibonding molecular orbitals (σ1s and σ2s) are also filled. This results in a bond order of 0, indicating no net bonding interaction between the two beryllium atoms. Consequently, Be₂ does not form a stable molecule under normal conditions.
Conclusion:
The key difference between Li₂ and Be₂ lies in their bond orders. Li₂ has a bond order of 1, signifying a stable bond, while Be₂ has a bond order of 0, indicating instability. This difference arises from the specific electron configurations and the resulting molecular orbital interactions in each molecule.