Stoichiometric
Index
A material is said to be stoichiometric when its composition corresponds exactly to its chemical formula. It may contain the lattice point defects required by thermodynamics at any finite temperature, but should not contain significant amounts of impurities. In a material such as the ionic solid NaCl (sodium chloride) the requirement for stoichiometry implies that the Na+ and Cl- ions are present in the ratio 1:1. For the ionic solid CaF2, the stoichiometric composition (which is also charge neutral) requires the Ca2+ and F- ions are present in the ratio 1:2