It follows from the Nernst theorem that, if we arbitrarily ascribe the value zero to
the entropies of elements in their perfect crystalline form at T = 0, then all perfect crystalline
compounds also have zero entropy at T = 0 (because the change in entropy that
accompanies the formation of the compounds, like the entropy of all transformations
at that temperature, is zero). This conclusion is summarized by the Third Law of
thermodynamics: