Asked in all five years, usually straight after the shape question and often worth Merit or Excellence. This is why SF₆ and PF₅ are non-polar despite very polar S–F and P–F bonds: their symmetrical shapes point the dipoles in directions that cancel exactly. Add a lone pair or swap one atom and the symmetry breaks. Worked example SF₄ polarity (2025) Identify and explain the polarity of SF₄, which is seesaw-shaped. S–F bonds are polar: fluorine is much more electronegative than sulfur, so each bond has a dipole pointing towards F. The shape is seesaw, not symmetrical, because a lone pair occupies one equatorial position. The bond dipoles therefore do not cancel; they sum to a net dipole pointing away from the lone pair. ✓ SF₄ is polar: polar bonds in an asymmetrical (seesaw) arrangement, so the dipoles do not cancel. ✓
The structure the schedule rewards
Say all three things, in order: (1) the bonds are polar and why, (2) the shape and why it is or is not symmetrical, (3) therefore the dipoles do or do not cancel. Missing step 2 is what usually caps an answer at Achieved. ℹ
2024 asked it backwards
Given that BrCl₃ is polar, candidates had to work out which of two possible shapes (T-shaped or trigonal planar) it must have. Trigonal planar would cancel; T-shaped does not — so it is T-shaped. Be ready to run the reasoning in either direction.