Chapter 8 Bonding and Molecular Structure - 8-8 Bond and Molecular Polarity - Review & Check for Section 8-8 - Page 325: 2

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$BCl_3$: it is trigonal planar and even though its bonds are polar, the vectorial sum cancels out to zero. $PCl_3$: it is trigonal pyramidal, the vectorial sum doesn't cancel out. $POCl_3$ and $SCl_2O_2$, both have square planar geometries but their vectorial sums don't cancel out.