Ion-dipole effects vs. atomic radius

Bipolarity

When dissolved in water, which of the following ions will form stronger ion-dipole bonds with the water molecules? Li+ or Na+?

Both have roughly the same charge... Na has greater radius, but I don't see why or how that has any bearing on the problem.

Borek

Radius changes distance between charges.

Bipolarity

Quote by Borek

Radius changes distance between charges.

I'm sorry but could you please elaborate a little more on that?
Radius I guess does decrease the force between the metal ion and each water molecule (due to Coulomb's law), but it turns out that Li+ actually forms more bonds with water. Why is that?

Borek

Smaller ion means dipoles are closer to the charge, so the Coulomb force is larger.

dizam

I believe this has to do with the difference in electronegativity. Lithium has a higher electronegativity.

DrDu

Solvation is often treated within a simple model, the Born model, which treats the atom as a charged sphere inside the medium assumed to be continuous and described by its dielectric constant. The model is still used a lot to describe the solvation of proteins even today.
Confer e.g.
http://pchemandyou.blogspot.com/2008...solvation.html

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Bipolarity	Ion-dipole effects vs. atomic radius Tweet When dissolved in water, which of the following ions will form stronger ion-dipole bonds with the water molecules? Li+ or Na+? Both have roughly the same charge... Na has greater radius, but I don't see why or how that has any bearing on the problem.

Borek Admin	Ion-dipole effects vs. atomic radius Smaller ion means dipoles are closer to the charge, so the Coulomb force is larger.

dizam	I believe this has to do with the difference in electronegativity. Lithium has a higher electronegativity.

DrDu Recognitions: Science Advisor	Solvation is often treated within a simple model, the Born model, which treats the atom as a charged sphere inside the medium assumed to be continuous and described by its dielectric constant. The model is still used a lot to describe the solvation of proteins even today. Confer e.g. http://pchemandyou.blogspot.com/2008...solvation.html