Dilithium, Li₂, is a strongly electrophilic,

diatomic Diatomic molecules () are molecules composed of only two atoms, of the same or different chemical elements. If a diatomic molecule consists of two atoms of the same element, such as hydrogen () or oxygen (), then it is said to be homonuclear mol ...

molecule comprising two

lithium Lithium (from , , ) is a chemical element; it has chemical symbol, symbol Li and atomic number 3. It is a soft, silvery-white alkali metal. Under standard temperature and pressure, standard conditions, it is the least dense metal and the ...

atom Atoms are the basic particles of the chemical elements. An atom consists of a atomic nucleus, nucleus of protons and generally neutrons, surrounded by an electromagnetically bound swarm of electrons. The chemical elements are distinguished fr ...

s covalently bonded together. Li₂ has been observed in the gas phase. It has a

bond order In chemistry, bond order is a formal measure of the multiplicity of a covalent bond between two atoms. As introduced by Gerhard Herzberg, building off of work by R. S. Mulliken and Friedrich Hund, bond order is defined as the difference between t ...

of 1, an internuclear separation of 267.3 pm and a

bond energy In chemistry, bond energy (''BE'') is one measure of the strength of a chemical bond. It is sometimes called the mean bond, bond enthalpy, average bond enthalpy, or bond strength. IUPAC defines bond energy as the average value of the gas-phase b ...

of 102 kJ/mol or 1.06 eV in each bond.''Chemical Bonding'', Mark J. Winter, Oxford University Press, 1994, The

electron configuration In atomic physics and quantum chemistry, the electron configuration is the distribution of electrons of an atom or molecule (or other physical structure) in atomic or molecular orbitals. For example, the electron configuration of the neon ato ...

of Li₂ may be written as σ². Being the third-lightest stable neutral

homonuclear In chemistry, homonuclear molecules, or elemental molecules, or homonuclear species, are molecules composed of only one element. Homonuclear molecules may consist of various numbers of atoms. The size of the molecule an element can form depends ...

diatomic molecule Diatomic molecules () are molecules composed of only two atoms, of the same or different chemical elements. If a diatomic molecule consists of two atoms of the same element, such as hydrogen () or oxygen (), then it is said to be homonuclear mol ...

(after

dihydrogen Hydrogen is a chemical element; it has symbol H and atomic number 1. It is the lightest and most abundant chemical element in the universe, constituting about 75% of all normal matter. Under standard conditions, hydrogen is a gas of diatom ...

and dihelium), dilithium is an extremely important model system for studying fundamentals of physics, chemistry, and electronic structure theory. It is the most thoroughly characterized compound in terms of the accuracy and completeness of the empirical potential energy curves of its electronic states. Analytic empirical potential energy curves have been constructed for the X-state, a-state, A-state,W. Gunton, M. Semczuk, N. S. Dattani, K. W. Madison, ''High resolution photoassociation spectroscopy of the ⁶Li₂ A-state'', https://arxiv.org/abs/1309.5870 c-state, B-state, 2d-state, l-state, E-state, and the F-state. The most reliable of these potential energy curves are of the Morse/Long-range variety (see entries in the table below). Li₂ potentials are often used to extract atomic properties. For example, the C₃ value for atomic lithium extracted from the A-state potential of Li₂ by Le Roy et al. in is more precise than any previously measured atomic oscillator strength. This lithium oscillator strength is related to the radiative lifetime of atomic lithium and is used as a benchmark for atomic clocks and measurements of fundamental constants.

See also

References

Further reading