# hydrated halide structure

What is the structure of $\ce{LiCl.2H2O}$? I think when $\ce{LiCl}$ is put in aqueous medium, it will break into $\ce{Li+}$ and $\ce{Cl-}$. Then $\ce{H2O}$ will give LP to Li and hydrate it. But why 2 $\ce{H2O}$ molecules? 2 means 2 coordinate bonds? Octet is not filled? Then why does this happen?

• Crystal structures in general are not the kind of thing you can deduce through logic alone. There is no simple answer to "why are there $2\ce{H2O}$". Also, $\ce{LiCl}$ has other hydrates as well. – Ivan Neretin Dec 14 '15 at 21:03
• So it's like an ionic bond between Li+ ans Cl- and 2 coordinate bonds by water to Li+? – Shodai Dec 15 '15 at 9:25
• So we don't know and have no way of knowing what is it like, unless we look up the actual structure in a database. – Ivan Neretin Dec 15 '15 at 9:43

The radius ratio of $\ce{Li+}$ and $\ce{Cl-}$ is very small, this means the size of $\ce{Li+}$ is so small than $\ce{Cl-}$ that the crystal lattice of $\ce{LiCl}$ becomes unstable. So to make the size of $\ce{Li+}$ bigger $\ce{H2O}$ molecules surround the caption bigger and make the structure stable.