Which one of the following could exist in both polar and no polar forms?

Depending on their arrangement.

Answer

If you are like me you know the structure straightaway but that comes from many years of experience. So: (a) XeFCl linear F more electronegative that Cl so polar. b) Let’s leave till last c) SiCl2F2 AX4 tetrahedral only one isomer (cf CH2Cl2) F more electronegative than Cl so polar (Si-Fδ-→ vectors do not cancel). d) SCl2F2 AX4E see saw as soon as you have only one lone pair it is polar no matter the isomers (3). e) PCl2F AX3 trigonal pyramidal one isomer with lone pair: polar. (b) XeCl2F2 AX4E2 square planar can have cis (polar Xe-Fδ-→ vectors do not cancel) and trans iomers (non polar; Xe-Fδ-→ vectors cancel). The only problem is XeF2Cl2 is I believe unknown. I’ll check. The operative word is “could.” Yes it is unknown assumed to dec to XeF2 and Cl2.