# Question #9ce37

We often write ${M}^{n +} \left(a q\right)$ to represent a metal ion in solution. By this we mean the $\text{aquated complex}$, the coordination complex if you like between the ${M}^{n +}$ ion and several water ligands.
So when we write $F {e}^{2 +} \left(a q\right)$ or $N {a}^{+} \left(a q\right)$ we mean the hexaqua complexes, ${\left[F e {\left(O {H}_{2}\right)}_{6}\right]}^{2 +}$ or ${\left[N a {\left(O {H}_{2}\right)}_{6}\right]}^{+}$. The oxygen atom has lone electron pairs, and clearly acts as the donor, i.e. as the base, towards a Lewis-acidic metal cation.