Question

What is necessary for a bond to be considered polar?

What is necessary for a molecule to be polar?

Answer 1

Non - Polar bonds :

A bond between 2 nonmetal atoms that have the same electronegativity and therefore have equal sharing of the bonding electron pair Nonpolar Covalent Bond

Example: In H-H each H atom has an electronegativity value of 2.1, therefore the covalent bond between them is considered nonpolar

Polar Covalent Bond

A bond between 2 nonmetal atoms that have different electronegativities and therefore have unequal sharing of the bonding electron pair

Example : In H-Cl, the electronegativity of the Cl atom is 3.0, while that of the H atom is 2.1

The result is a bond where the electron pair is displaced toward the more electronegative atom. This atom then

obtains a partial-negative charge while the less electronegative atom has a partial-positive charge.This separation

of charge or bond dipole can be illustrated using an arrow with the arrowhead directed toward the more

electronegative atom.

The Greek letter delta indicates "partially".

Within a molecule each polar bond has a bond dipole

A polar molecule always contains polar bonds, but some molecules with polar bonds are nonpolar.

Polar Molecule

A molecule in which the bond dipoles present do not cancel each other out and thus results in a molecular dipole.Cancellation depends on the shape of the molecule or Stereochemistry and the orientation of the polar bonds.

Molecular Dipole

A result of the bond dipoles in a molecule.

Bond dipoles may or may not cancel out thereby producing either molecules that are nonpolar, if they cancel, or polar, if they do not cancel

• Examples: CO₂ is a linear molecule with 2 bond dipoles that are equal and oppositely directed therefore the bond polarities cancel and the molecule is nonpolar.

HCN is a linear molecule with 2 bond dipoles that are in the same direction and are not equal therefore the bond polarities do not cancel and the molecule is polar