Question

Question #d676f

Answer 1

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

Explanation:

The polarity of a covalent bond `"X—Y"` is determined by the electronegativity difference `ΔEN` between the atoms `"X"` and `"Y"`.

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

For example, `"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, `"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, `"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 `"C—H"` bond,

`ΔEN = "|2.55 - 2.20|" = 0.35`

Thus, a `"C—H"` bond is often called nonpolar even though it is very slightly polar.