[Argus]

Recently, I saw something that puzzled me:
NaPO₄ . H₂O

This is a complex ion, right?

How/where are the water molecules attatched.  To the P?  I think not because that would leave P in an unstable and I think impossible state with seven bonds.  However, the P ion does have an empty electron shell which means it can act as a lewis acid. But that can't be right either because just because it has an empty shell doesn't mean it can bond, in fact it means quite the opposite.

Just when I thought I knew all about orbitals and the like, along came these complex ions and wierd configurations like Cr and Ag!

Would someone be kind enough to explain (in terms of orbitals please) complex ions, and how you can have the central thing (I forget its special name) can be larger than a single atom?  Also, well you're at it, complex ions and coordnation chemistry in general because the sites aren't quite adequate.

Thank you so much!

[jdurg]

NaPO₄.H₂O isn't really a complex ion.  It's just a hydrated salt.  What the formula means is that for every occurance of sodium phosphate, there is one water molecule "stuck" in the crystal.  The '.H2O' indicates the presence of a water molecule in the crystal structure of the salt.  So when the salt forms from solution, a water molecule winds up in the crystal structure for every molecule of sodium phosphate.  (And I do believe that the formula should be Na₃PO₄.H₂O).