Homonuclear diatomic molecules & their Electronic Configuration Notes | Study Physical Chemistry - Chemistry

What are Diatomic molecules?

Molecules formed upon the bonding of two same elements are known as homonuclear diatomic molecules. For example dihydrogen (H₂), dinitrogen (N₂), etc. In this article, we will study the formation of these diatomic molecules, their stability, and other characteristics.

Some common diatomic molecules

• Hydrogen molecule (H₂): Dihydrogen molecule belongs to the family of diatomic molecules, which consists of two hydrogen atoms bonded to each other by a covalent bond. According to the atomic number of hydrogen, it has only one electron in its 1s orbital. The electronic configuration of H₂ molecule is given as:
  H₂: (σ1s)²
  Bond order =  =  = 1
  Due to the absence of unpaired electrons in the hydrogen molecule, it is diamagnetic in nature.
• Lithium molecule (Li₂): Lithium molecule belongs to the family of diatomic molecules, which consists of two lithium atoms, bonded to each other by a covalent bond. The electronic configuration of Li₂ molecule is given as:
  Li₂: (σ1s)² (σ*1s)² (σ2s)²
  Bond order == 1
  Thus the Li₂ molecule is stable and is diamagnetic in nature due to the absence of unpaired electrons.
• Carbon molecule (C₂): Carbon molecule belongs to the family of diatomic molecules, which consists of two carbon atoms, bonded to each other by a covalent bond. The electronic configuration of the Carbon molecule is given as,
  C₂ :(σ1s)² (σ*1s)²(σ2s)² (σ *2s)² (π2p²_x= π 2p²_y)
  Bond order = = 2
  Due to the absence of unpaired electrons, C₂ is diamagnetic in nature. Furthermore, due to the presence of four electrons in pi bonding orbitals, the double bond in C₂ consists of both pi bonds.
• Oxygen molecule (O₂): Oxygen molecule belongs to the family of diatomic molecules, which consists of two oxygen atoms, bonded to each other by a covalent bond. The electronic configuration of the Oxygen molecule is given as,
  O₂: (σ1s)² (σ*1s)² (σ2s)² (σ *2s)² (σ2p_z) ² (π2p²_x= π 2p²_y) (π*2p¹_x= π*2p¹_y)
  Bond order = = 2.
  Due to the presence of one unpaired electron, O₂molecule should be paramagnetic.
• Helium molecule (He₂): According to the atomic number of helium, it has two electrons in 1s.The electronic configuration of the helium molecule  according to molecular orbital theory is given as:
  He₂: (σ1s)² (σ*1s)²
  Bond order == 0.
  Thus, He₂  molecule is unstable and does not exist.