Aluminum oxide (Al2O3) is a compound formed by the combination of aluminum and oxygen. Aluminum nitrate (Al(NO3)3) is a compound formed by the combination of aluminum and nitrate ions. Aluminum hydroxide (Al(OH)3) is a compound formed by the combination of aluminum and hydroxide ions.

In terms of relative strength, aluminum oxide is the strongest compound among the three, followed by aluminum nitrate and then aluminum hydroxide. This is because aluminum oxide is an ionic compound with strong bonds between aluminum and oxygen ions, while aluminum nitrate and aluminum hydroxide are both salts that can dissociate in water and have weaker bonds compared to aluminum oxide.