When aluminium (Al) reacts with oxygen (O2), it undergoes a highly exothermic reaction, resulting in the formation of aluminium oxide (Al2O3). This reaction is typically observed during the combustion of aluminium. The chemical equation for this reaction is:

4Al(s) + 3O2(g) → 2Al2O3(s)

In this reaction, four moles of solid aluminium react with three moles of oxygen gas to produce two moles of solid aluminium oxide. The process involves the transfer of electrons from aluminium atoms to oxygen atoms, leading to the formation of strong ionic bonds within the aluminium oxide compound.

During the reaction, a significant amount of heat is released in the form of light and heat energy. This exothermic nature of the reaction makes it useful in various industrial applications, such as welding and cutting metals. The intense heat produced can melt and fuse metals together, making it a valuable tool in metalworking processes.

Aluminium oxide, the product of this reaction, is a white, hard, and refractory material. It is commonly known as alumina and finds applications in various industries, including abrasives, high-temperature ceramics, and as a catalyst in chemical processes.