Trinitrogen also known as the azide radical is an unstable molecule composed of three

nitrogen Nitrogen is a chemical element; it has Symbol (chemistry), symbol N and atomic number 7. Nitrogen is a Nonmetal (chemistry), nonmetal and the lightest member of pnictogen, group 15 of the periodic table, often called the Pnictogen, pnictogens. ...

atoms. Two arrangements are known: a linear form with double bonds and charge transfer, and a cyclic form. Both forms are highly unstable, though the linear form is the more stable of the two. More-stable derivatives exist, such as when it acts as a

ligand In coordination chemistry, a ligand is an ion or molecule with a functional group that binds to a central metal atom to form a coordination complex. The bonding with the metal generally involves formal donation of one or more of the ligand's el ...

, and it may participate in azido nitration, which is a reaction between

sodium azide Sodium azide is an inorganic compound with the formula . This colorless salt is the gas-forming component in some car airbag systems. It is used for the preparation of other azide compounds. It is highly soluble in water and is acutely poisonou ...

and ammonium cerium nitrate. The linear form of N₃ was discovered in 1956 by B. A. Thrush by

photolysis Photodissociation, photolysis, photodecomposition, or photofragmentation is a chemical reaction in which molecules of a chemical compound are broken down by absorption of light or photons. It is defined as the interaction of one or more photons wi ...

hydrogen azide Hydrazoic acid, also known as hydrogen azide, azic acid or azoimide, This also contains a detailed description of the contemporaneous production process. is a compound with the chemical formula . It is a colorless, volatile, and explosive liquid ...

. As a linear and symmetric molecule, it has D_∞h symmetry, with a nitrogen–nitrogen

bond length In molecular geometry, bond length or bond distance is defined as the average distance between Atomic nucleus, nuclei of two chemical bond, bonded atoms in a molecule. It is a Transferability (chemistry), transferable property of a bond between at ...

averaging 1.8115 Å. The first excited electronic state, A²Σ_u, is 4.56 eV above the ground state. The cyclic form was identified in 2003 by N. Hansen and A. M. Wodtke using

ultraviolet Ultraviolet radiation, also known as simply UV, is electromagnetic radiation of wavelengths of 10–400 nanometers, shorter than that of visible light, but longer than X-rays. UV radiation is present in sunlight and constitutes about 10% of ...

photolysis of chlorine azide. Although the reaction yielded mostly the linear form, about 20% of the molecules were cyclic. The ring has C_2v symmetry—an isosceles triangle—in contrast to the linear form that has equal N–N bond-lengths.

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* {{Triatomic elements Homonuclear triatomic molecules Nitrogen compounds Allotropes of nitrogen