# Question #81a83

We write $A {l}^{3 +}$. In aqueous solution, this is likely the coordination complex ${\left[A l {\left(O {H}_{2}\right)}_{6}\right]}^{3 +}$. Aluminum forms (i) the smallest cation, and it is certainly the most charge dense, and thus the most likely to draft in solvent molecules to satisfy its Lewis acidity. Anions can be hydrated to some extent. However, the oxide anion would have only a transient existence in water; $B {r}^{-}$ is probably surrounded by 4-6 water solvent molecules.