What is the common oxidation state of aluminum in its compounds?

The common oxidation state of aluminum in its compounds is +3. This is due to the fact that aluminum has three electrons in its outermost energy level (the third shell). To achieve a stable electron configuration similar to that of the noble gases, aluminum tends to lose these three valence electrons when it forms compounds, resulting in a +3 charge.

In many aluminum compounds, such as aluminum oxide (Al2O3) and aluminum chloride (AlCl3), aluminum exhibits this +3 oxidation state, which is a defining characteristic of its chemistry. This preference for the +3 oxidation state is also characteristic of metals found in Group 13 of the periodic table.

Understanding this oxidation state is crucial for predicting the behavior of aluminum in various chemical reactions and understanding its role in different compounds.