Aluminium fluoride(m.p. 1291˚C) and phosphorous trifluoride (m.p. -151˚C) have very different physical ...?

Question

properties. Draw dot & cross diagrams to illustrate the bonding in these compounds, and hence explain the difference in their melting points.

You dont have to draw the d&t diagram. Thanks.

Answer 1

If you've drawn the diagrams properly, then you will see that AlF3 is an ionic compound, with widespread electrostatic attractive forces to match, whereas PF3 is a covalent simple molecule, with only dipole-dipole forces to keep the molecules weakly attracted to each other.