The atomic volume of hydrogen in metal hydrides in comparison with corresponding fluorides and chlorides

The atomic volume of hydrogen in metal hydrides is calculated by using the atomic volumes of the metal cations as given by Biltz. The exceptional polarizability of hydrogen ligands is the reason for its adaptability when forming different bond structures in metal hydrides. The atomic volume of hydrogen decreases from 13.7 cm(3)mol(-1) in salt-like caesium hydride to 3.9 cm(3)mol(-1) in metallic palladium hydride. This variation is significantly higher for metal hydrides than for metal chlorides, although the volume of a hydrogen ion is comparable to that of a fluoride ion, that shows an almost constant value in its compounds. For structurally related hydrides an examination of the atomic volume of hydrogen allows the re-examination of a given composition and therefore the disclosure of a wrong atomic arrangement.