[lizval]

why do people say that rock salt structure is two Interpenetrating FCC Structures if sodium has a body-centred cubic and chlorine has an orthorhombic structure? thank U

[mjc123]

Salt is not a mixture of (elemental) sodium and chlorine. It is a compound, with completely different properties. It consists of Na⁺ and Cl^- ions, not Na atoms and Cl₂ molecules, and its crystal structure has no relation at all to those of elemental sodium and chlorine.