page_title: Molecular orbital diagram
section_title: Dilithium
hierarchical_section_title: Molecular orbital diagram / Diatomic MO diagrams / Dilithium
caption_attribution_description: English: MO diagram dilithium molecule
context_page_description: A molecular orbital diagram, or MO diagram, is a qualitative descriptive tool explaining chemical bonding in molecules in terms of molecular orbital theory in general and the linear combination of atomic orbitals method in particular. A fundamental principle of these theories is that as atoms bond to form molecules, a certain number of atomic orbitals combine to form the same number of molecular orbitals, although the electrons involved may be redistributed among the orbitals. This tool is very well suited for simple diatomic molecules such as dihydrogen, dioxygen, and carbon monoxide but becomes more complex when discussing even comparatively simple polyatomic molecules, such as methane. MO diagrams can explain why some molecules exist and others do not. They can also predict bond strength, as well as the electronic transitions that can take place.
context_section_description: MO theory correctly predicts that dilithium is a stable molecule with bond order 1 (configuration 1σg²1σᵤ²2σg²). The 1s MOs are completely filled and do not participate in bonding.
  Dilithium is a gas-phase molecule with a much lower bond strength than dihydrogen because the 2s electrons are further removed from the nucleus. In a more detailed analysis which considers the environment of each orbital due to all other electrons, both the 1σ orbitals have higher energies than the 1s AO and the occupied 2σ is also higher in energy than the 2s AO (see table 1).
caption: MO diagram of dilithium
exif: {}