This colourless solid is prepared by the reaction of selenium with a solution of sodium in liquid ammonia at −40 °C.

Like other alkali metal chalcogenides, this material is highly sensitive to water, easily undergoing hydrolysis to give mixtures of sodium biselenide (NaSeH) and hydroxide.

This hydrolysis occurs because of the extreme basicity of the Se2− ion.

Similarly, sodium selenide is readily oxidized to polyselenides, a conversion signaled by off-white samples.

With alkyl halides, one obtains a variety of organoselenium compounds: Organotin and organosilicon halides react similarly to give the expected derivatives: