Ball-and-stick model of the coordination geometry of the potassium cation in the crystal structure of the α of potassium nitrate, KNO₃, i.e. [K⁺][NO₃⁻].

The compound was originally thought to adopt a simple, highly symmetric structure in space group Pmcn but has recently been found to crystallise in the lower symmetry space group Cmc2₁. This means there are three slightly different (crystallographically independent) environments for each potassium ion and for each nitrate ion. Despite their formal independence, diagrams of these environments look identical, so only one of them has been depicted here.

The structure was reported in Acta Crystallogr. C (2003) 59, i139–i140 and is available as COD entry 2013633, CSD entry 1722034 and ICSD entry 281552.

Colour code:

  Potassium, K: purple

  Nitrogen, N: blue

  Oxygen, O: red