# Why are aqua ion complexes of transition elements not solid but a solution? [closed]

Water ligands form dative covalent bonds with the central transition metal ion. That would mean a molecule is formed, just like sulfur dioxide or any other.

The transition metal ion does not form dipole ion attraction with water as does sodium chloride, but forms a covalent bond. If so, why is the resulting mixture a solution, and not a solid?

• You have it all backwards. Solutions of transition metal salts are not all that different from the solution of NaCl. Besides, a hydrated transition metal ion may be a part of a solid all right. – Ivan Neretin Nov 3 '17 at 5:07
• For some reason it keeps getting repeated that transition metals dissolved in water were conceptionally different in any way to sodium chloride dissolved in water. This is not the case! Sodium also undergoes complex formation with water molecules. The difference to many (but not all) transition metals is that the complexes are structurally highly fluctional and thus not well defined. – Jan Nov 20 '17 at 9:49

Whether or not the complex ion (e.g. $\ce{[Fe(H2O)6]^2+}$) is in solution or in a solid depends on what you did with the compound. A lot of hydrates are actually cationic aquacomplexes; for example, solid $\ce{CuSO4.5H2O}$ can be described as $\ce{[Cu2(H2O)8(\mu{-}SO4)2] . 2H2O}$ instead, showing that we have complexes in the solid state, too.