Question #d676f

1 Answer
Oct 3, 2017

Answer:

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.