To determine which pair of elements would form the least polar bonds, we can look at the differences in their electronegativities. The smaller the difference, the less polar the bond.
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Bromine and Nitrogen:
Electronegativity difference = |2.8 - 3.0| = 0.2 -
Phosphorus and Bromine:
Electronegativity difference = |2.1 - 2.8| = 0.7 -
Nitrogen and Oxygen:
Electronegativity difference = |3.0 - 3.5| = 0.5 -
Oxygen and Phosphorus:
Electronegativity difference = |3.5 - 2.1| = 1.4
From these calculations, the pair that forms the least polar bonds is bromine and nitrogen, with an electronegativity difference of only 0.2.