Orthonitrate is a tetrahedral

oxoanion An oxyanion, or oxoanion, is an ion with the generic formula (where A represents a chemical element and O represents an oxygen atom). Oxyanions are formed by a large majority of the chemical elements. The formulae of simple oxyanions are determined ...

of nitrogen with the formula . It was first identified in 1977 and is currently known in only two compounds, sodium orthonitrate (Na₃NO₄) and potassium orthonitrate (K₃NO₄). The corresponding oxoacid, orthonitric acid (H₃NO₄), is hypothetical and has never been observed. Sodium and potassium orthonitrate can be prepared by fusion of the nitrate and metal oxide under high temperatures and ideally high pressures (several

GPa Grading in education is the process of applying standardized measurements for varying levels of achievements in a course. Grades can be assigned as letters (usually A through F), as a range (for example, 1 to 6), as a percentage, or as a numbe ...

). :NaNO₃ + Na₂O → Na₃NO₄ (300 °C for 3 days) The resulting orthonitrates are white solids which are extremely sensitive to moisture and CO₂, decomposing within minutes to sodium hydroxide, sodium carbonate, and sodium nitrate upon exposure to air. :Na₃NO₄ + CO₂ → NaNO₃ + Na₂CO₃ :Na₃NO₄ + H₂O → NaNO₃ + 2 NaOH The orthonitrate ion is tetrahedral with N–O bond lengths of 139 pm, which is unexpectedly short, indicating that polar interactions are shortening the bond. This short bond length parallels that of oxoanions containing third-row elements like and , for which pπ–dπ bonding was previously proposed as the explanation for the short bond length. Since 3d orbitals of nitrogen are much too high in energy to be involved in the case of orthonitrate, the shortness of the N–O bond in orthonitrate indicates that pπ–dπ bonding is likely not the most important explanation for the bond lengths of these heavier anions either. (''See the article on''

hypervalence In chemistry, a hypervalent molecule (the phenomenon is sometimes colloquially known as expanded octet) is a molecule that contains one or more main group elements apparently bearing more than eight electrons in their valence shells. Phosphorus pe ...

''for a discussion of bonding models'')

Other nitrogen oxoanions

nitrate Nitrate is a polyatomic ion with the chemical formula . Salts containing this ion are called nitrates. Nitrates are common components of fertilizers and explosives. Almost all inorganic nitrates are soluble in water. An example of an insolubl ...

, *

nitrite The nitrite ion has the chemical formula . Nitrite (mostly sodium nitrite) is widely used throughout chemical and pharmaceutical industries. The nitrite anion is a pervasive intermediate in the nitrogen cycle in nature. The name nitrite also re ...

References

{{Nitrogen compounds Oxyanions Nitrates