Tetravalent titanium compouds like TiCl4 are generally covalent, rather than ionic. If we look at the difference in the electronegativity of titanium and chlorine, we have 3.0 - 1.5 = 1.5. This is less of a difference than that in sodium chloride, 3.0 - 0.9 = 2.1. In general, if the electronegativity difference D is 2.0 or greater we have ionic bonding, D between about 0.5 and 2.0 is a polar covalent bond, and D less than 0.5 is a nonpolar covalent bond.
Next we look at the molecular geometry of TiCl4, which is tetrahedral. Thus, the molecule is nonpolar overall, despite having those polar Ti-Cl bonds. Strong dipole-dipole interactions between the molecules therefore are not present, just the much weaker London dispersion interactions.
For more dramatic examples, look at SF6, SeF6, and TeF6, which are gases at room temperature! It would be interesting to know what the highest molecular weight gaseous compound known is (at room temperature and pressure).
Steve
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