Question

For each of the following: draw the Lewis structure (use o whenever possible), name the molecular shape, and indicate if it is polar or nonpolar. 

a. SBr2 b. BrH3 c. SiF4 d. H2O

e. CH3F f. SiO2 g. SO2 h. NI3

Answer 1

Polar molecules are those molecules having polar bonds. Covalent bonds having a considerable electronegativity difference are termed polar bonds. Polar bonds have partial positive character towards one end, and negative character towards the other. If two polar bonds are symmetrically placed opposite to each other, the dipole moment cancels out and the molecule becomes nonpolar.

a. SBr₂ : has polar S-Br bonds. but as they are placed at an angle of 180⁰, they cancel each other resulting in nonpolarity of the molecule.

b. Polar, as the dipole due to the left and right Br-H bonds are cancelled as they are opposite to each other. But the dipole moment due to the Br-H bond towards down is not cancelled, moreover, the presence of 2 lone pairs make the molecule polar.

c. SiF₄: has 4 polar bonds placed at the alternate corners of a cube, thus cancelling each other. Thus, the moleculae is nonpolar

d. In H₂O, the two polar O-H bonds are kept in an angle which is not 180⁰, thus there is a net dipole moment.

e. The positions if the bonds are as same as (c). But the magnitude dipole moment of C-F bond is higher than that of C-H bond.

f. Same discussion as (a).

g. same discussion as (d)

h. NI₃ : same discussion as (b)