Question

For each bond, show the direction of polarity by placing a + sign next to the atom expected to have a partial positive charge and a − sign next to the atom expected to have a partial negative charge. (A) __?__ Te-Se __?___ (B) _?__ O-Te __?_ (C) __?__ O-Se __?__ The most polar bond is ____ (A,B, or C)

Answer 1

The direction of polarity is related to the electronegativity. In a dipole, the element with greater electronegativity will acquire slight negative (δ-) charge. We can predict the type of bond based upon electronegativity differences:

1) If the difference in electronegativities is 0 then the bond is non-polar covalent e.g. - H₂ bond

2) If the difference in electronegativities is between 0 and 1.9 then the bond is polar covalent e.g. - HCl bond. The electronegativities of H and Cl are 2.1 and 3.0, respectively. Therefore, the difference in electronegativity is 0.9.

3) If the difference in electronegativities is greater than 2.0 then the bond is ionic. e.g. - LiCl bond. The electronegativities of Li and Cl are 1.0 and 3.0, respectively. Therefore, the difference in electronegativity is 2.0.

The electronegativities of Te, Se and O are 2.1, 2.4 and 3.5, respectively. Therefore, in Te-Se bond Se will a acquire δ- charge while Te will acquire δ+ charge. The difference in electronegativities is 0.3 and hence Te-Se bond is polar covalent bond. Similarly, in O-Te bond O will a acquire δ- charge while Te will acquire δ+ charge. The difference in electronegativities is 1.4 and hence O-Te bond is polar covalent bond. In O-Se bond O will a acquire δ- charge while Se will acquire δ+ charge. The difference in electronegativities is 1.1 and hence O-Se bond is polar covalent bond.

The difference in electronegativities is greater for O-Te bond and least for Te-Se bond. Hence, O-Te bond is the most polar bond while Te-Se is the least polar bond among the three bonds.