Lux - Flood Concept (1939 & 1947) :
(i) The proton plays an important role in explaining the acid-base behaviour in the Bronsted-Lowery concept. Lux observed that acid - base reactions are also feasible in oxide systems without the aid of protons.
(ii) Above approach was extended by Flood and applied to non-protonic systems, which were not covered by the Bronsted Lowery concept.
(iii) According to this concept a base (like CaO, BaO or Na2O) is an oxide ion (O2–) donor and an acid (like SiO2 , CO2 or P4 O10) is an oxide ion (O2–) acceptor.
(iv) Substances are termed amphoteric if they show a tendency of losing as well as accepting an oxide ion.
Ex: ZnO, Al2O3
Note :
(i) The concept is particularly applicable to reactions which take place at high temperature i.e. in metallurgical operations or during the manufacture of ceramics and glass.
(ii) The approach can be extended to include other negative ion systems (like halides, sulphide or carbanion).
