Cation Solubility

1. Sep 29, 2005

Tom McCurdy

I was wondering if their is a reltionship between cation solubility and the poistion of its element in the periodic table?

2. Sep 29, 2005

bomba923

Not that simple. Aqueous solubility depends on the anion as well.

For example, $${\text{Ca}}\left( {{\text{NO}}_{\text{3}} } \right)_{\text{2}}$$ is (obviously) soluble, whereas both $${\text{CaSO}}_{\text{4}}$$ and $${\text{CaCO}}_{\text{3}}$$ are insoluble (dissolve in small and likely insignficant amounts in water). All nitrates are generally soluble and carbonates are generally insoluble.

There are cases where the cation position on the periodic table does matter. For example, both $${\text{Be}}\left( {{\text{OH}}} \right)_2$$ and $${\text{Mg}}\left( {{\text{OH}}} \right)_2$$ are considered insoluble, whereas $${\text{Ca}}\left( {{\text{OH}}} \right)_2$$ and the heavier alkalines are soluble.

*Generally, what you observe is a longer ionic single bond length for heavier cations, which will take successively less energy to dissociate going down a group of the periodic table. (that said, I'm pretty sure that double-bonded MgO is insoluble).

For some of the rules of solubility, click http://chemed.chem.purdue.edu/genchem/topicreview/bp/ch18/soluble.html#rules [Broken]! )
-Hope this helps

Last edited by a moderator: May 2, 2017
3. Sep 30, 2005

GCT

perhaps you're referring to the hydrated radii of a cation, I think that you may be able to correlate this with its trends in ionic strength, and then with the activity (perhaps with a plot of activity v.s. increasing formal concentration); if at suitable concentrations by using the debye huckel equation. There may be a better way, or even a standard method. You may want to researcht the d-b equation.

4. Oct 3, 2005