NaH is colorless, although samples generally appear grey. NaH is around 40% denser than Na (0.968 g/cm).
NaH, like LiH, KH, RbH, and CsH, adopts the NaCl crystal structure. In this motif, each Na ion is surrounded by six H centers in an octahedral geometry. The ionic radii of H (146 pm in NaH) and F (133 pm) are comparable, as judged by the Na−H and Na−F distances.