Question

Predict which molecules are polar. Select all that apply. AsF3 IOF5 CF4 CH2CI2

Answer 1

Concepts and reason

Polarity means a charge separation between two poles in the molecule or the oppositely charged poles connected through a bond. Polarity occurs in molecules due to their electronegativity difference between atoms in a bond.

Fundamentals

• Polarity in molecules mainly depends on the electronegativity of their atoms and the geometry of the molecule.

• If the molecule is having symmetrical geometry and equal dipole moments for bonds, then the molecule is considered as nonpolar molecule.

• If the molecule is having unsymmetrical geometry and equal dipole moments for bonds, then the molecule is considered as polar molecule.

Example: Assume that Y is more electronegative atom than X.

Symmetrical geometry which is nonpolar is shown below:

Unsymmetrical geometry which is polar is shown below:

• Electronegativity of an atom is a tendency to attract the bonded pair of electrons towards itself.

Element	Electronegativity
Carbon	2.5
Hydrogen	2.1
Chlorine	3.0
Oxygen	3.5
Fluorine	4.0
Iodine	2.5

The given molecule is ${\rm{As}}{{\rm{F}}_{\rm{3}}}$ , and the structure is drawn below:

The given molecule is polar molecule, since fluorine atom is more electronegative than As ,The net dipole moment is not equal to zero, it means that the given molecule is a polar molecule.

The given molecule is ${\rm{IO}}{{\rm{F}}_{\rm{5}}}$ , and the structure is drawn below:

Although the structural geometry of the molecule is symmetrical, the given molecule is a polar molecule. In this molecule, the plane iodine fluorine dipole moments cancel each other but the dipole moments of iodine-oxygen bond and iodine-fluorine bond do not cancel each other, since electronegative difference between the iodine and oxygen is more than the iodine and fluorine.

Therefore, the given molecule is a polar molecule

The given molecule is ${\rm{C}}{{\rm{F}}_{\rm{4}}}$ , and the structure is drawn below:

The given molecule is nonpolar molecule, since the molecular geometry of the given molecule is symmetrical and the dipole moments of bonds cancel that are opposites to each other.

Therefore, the given molecule is non-polar molecule.

The given molecule is ${\rm{C}}{{\rm{H}}_{\rm{2}}}{\rm{C}}{{\rm{l}}_{\rm{2}}}$ , and the structure is drawn below:

Although the given molecule is geometrically symmetrical, all the dipole moments are projected to the one end of the molecule. Therefore, given molecule is polar molecule.

The polar molecules are written below:

${\rm{As}}{{\rm{F}}_{\rm{3}}}$

${\rm{IO}}{{\rm{F}}_{\rm{5}}}$

${\rm{C}}{{\rm{H}}_{\rm{2}}}{\rm{C}}{{\rm{l}}_{\rm{2}}}$

The non-polar molecules are written below:

${\rm{C}}{{\rm{F}}_{\rm{4}}}$

Ans:

The polar molecules are shown below: