Sodium iodide ($\mathrm{NaI}$)

Sodium iodide is the ionic salt $\mathrm{NaI}$, composed of sodium and iodide ions. In water, dissociation gives a source of iodide for chemical reactions.

A crystal of sodium iodide has quite different uses from an aqueous solution. Appropriately activated crystals can emit light when radiation deposits energy, enabling scintillation counters; the crystal's composition and activator concentration are part of the detector specification.