Re: IONS

["Ludwik Kowalski" <KowalskiL@Mail.Montclair.edu>]

On Sun, 20 Sep 1998, Patti Mason wrote:

> Technically, there is no such thing as a molecule of NaCl,
> because molecules are compounds with covalent bonding.
> The bonding in NaCl is ionic and the NaCl exists as ion
> pairs in the crystalline structure. Upon dissolving in water,
> dissociation occurs, not ionization. The ions were already
> there. Molecules which are covalently bonded such as HCl
> ionize upon dissolving in water.
>
> The water molecule is polar, having a partially positive
> end and a partially negative one. The water molecule can
> orient itself to "attack" either the positive sodium ion or
> the negative chloride ion and remove this ion from the
> crystal.

Pure NaCl may consist of ions but it is an insulator; the
ions will not move when an electric field is applied. The
same is true for the single "pseudo-molecule" of NaCl;
it is a neutral dipole. Pure water is also an insulator, its
relative dielectric constant is 81 (?). But we all know
that these two nonconductors make a good conductor,
when mixed. Nearly a paradox. A capacitor with pure
water between its plates would have 81 larger value of
C than an air capacitor (for the same geometry). I never
heard about water capacitors. Do they exist?

If water molecules can "remove" ions from crystals (and
from pseudo-molecules) then why don't they stick to them
forming (H2OCL-) and (H2ONA+) ions? Removal is due to an
attractive force; why is this force not able to bound such
ions? Most books refer Cl- and Na+ which are 18 units
lighter, and consequently more mobile.

Does anybody know what happens when a dielectric
material, such as glass, paraffin, or acrylic, is melted?
Is its conductivty reduced drastically? My guess is that
nothing drastic should happen to conductivities, for
example,  between 10 degrees below melting and 10
degrees above melting. But I am not sure. A reference
would be highly appreciated.
                                 Ludwik Kowalski