NaCl is the poster-compound for ionic bonding. The bonds in
NaCl have approximately 70% ionic character, making the bonds highly polar.
It's an exaggeration to say that there are real ions in NaCl with +1 and -1
charges, but the real charges of Na and Cl are certainly close to the expected
+1 and -1, correspondingly. Since NaCl is as a network of extremely charged
particles, and not separate molecules, NaCl does not display intermolecular
forces.
Water molecules conversely do display London dispersion forces, Keesom forces and
hydrogen bonding.
The polar water molecules are involved to the polarized Na and Cl atoms. This
is what permits NaCl(s) to dissolve and ionize in water. Consequently, the kind
of attraction accountable for the ionization of NaCl is ion-dipole attraction.
The ion - dipole attractions between the Na+ and the polar water molecule and the ion - dipole attractions between the Cl- and the polar water molecule contribute to the dissolution of sodium chloride in water.
Further Explanation:
Sodium chloride is an ionic compound. The electrostatic attraction between its positive charged ions (Na+) and negatively charged ions (Cl-) holds the crystal lattice together.
Water is a polar molecule. Polar molecules have a net dipole moment due to the differences in electronegativity of the atoms in the molecule and the geometry of the molecule as well. Since oxygen is more electronegative than hydrogen, it pulls the shared electrons towards itself. The part of the molecule where oxygen is, gains a partial negative charge, since the shared electrons spend more time in this region than near hydrogen. The hydrogen side of the molecule, then becomes mostly electron-deficient giving it a partial positive charge.
In the dissolution of sodium chloride in water, the ion - ion attractions of the salt is weakened as it absorbs heat. Then, polar water molecules start to surround individual Na+ or Cl- ions by orienting themselves accordingly: the partial negative side of water are attracted to the Na+ and the H side of the water molecule is attracted to the Cl- ions. With enough water molecules surrounding the each ion, the ion - dipole attractions formed overcome the ion - ion attraction of the salt.
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Keywords: dissolution, intermolecular forces
