# Question d676f

Oct 3, 2017

You calculate the difference in electronegativity between the two atoms in the bond.

#### Explanation:

The polarity of a covalent bond $\text{X—Y}$ is determined by the electronegativity difference ΔEN between the atoms $\text{X}$ and $\text{Y}$.

If the bond is between two identical atoms, the bond is covalent.

For example, $\text{F—F}$ is a covalent molecule.

ΔEN = "|3.98 - 3.98|" = 0

If ΔEN > 0, the bond is polar.

The values of ΔEN can range from 0 to about 3.1, so chemists have assigned arbitrary cut-off points.

Most chemists agree that a covalent bond is polar if ΔEN is between 0.5 and 1.6.

For example, $\text{H—Cl}$ is a polar covalent molecule.

ΔEN = "|2.20 - 3.16|" = 0.96

If ΔEN > 1.6, the bond is considered to be ionic.

For example, $\text{Na—Cl}$ is an ionic compound.

ΔEN = "|0.93 - 3.16|" = 2.23

Between 0 and 0.5, there is so little polarity that the bond is usually called nonpolar.

For a $\text{C—H}$ bond,

ΔEN = "|2.55 - 2.20|" = 0.35#

Thus, a $\text{C—H}$ bond is often called nonpolar even though it is very slightly polar.