Question

Using electronegativity values, determine bond polarities and the net dipoles in a molecule of PCl3 and indicate if the molecule will be polar.

Answer 1

1) determine molecular geometry:

valence electrons = 5+7*3 =26

Lewis structure:

number of bonding pairs = 3

number of lone pairs =1

general formula AB3X

electron geometry - tetrahedral

molecular geometry- trigonal pyramidal

Bond angle <109.5

2) Electronegativity: P - 2.1, Cl - 3.0

Difference in electronegativities |2.1-3.0|=|-0.9|= 0.9 Covalent polar

The molecule is polar as bonds are polar and dipole moments do not cancel out, as molecule does not have right geometry (like tetrahedral or trigonal planar).