Electronegativity And Polar Covalent Bonds Worksheet With Answers printable pdf download

Electronegativity And Polar Covalent Bonds Worksheet With Answers

ChemActivity 1.2: Electronegativity and Polar Covalent Bonds

Now that we know how to draw bonds between molecules, we’re going to learn more about the

chemical bond itself. When looking at a chemical bond, you might ask, “Are the electrons

equally shared between to two atoms or does one atom have more electron density closer to it

than another?” To answer this question, we must first look at the electronegativity of each atom.

Electronegativity: measure of how tightly an atom holds on to its electrons

Table 1.1 Electronegativity Values of Some Common Elements

Increasing electronegativity

2.1

1.0

1.5

2.0

2.5

3.0

3.5

4.0

Increasing

electronegativity

0.9

1.2

1.5

1.8

2.1

2.5

3.0

0.8

2.8

Chemists classify bonds into three different categories: (1) covalent bonds, (2) polar covalent

bonds, and (3) ionic bonds. To determine what type of bond is formed between two atoms you

must determine the difference in electronegativity between the two atoms in the bond.

If the ΔEN (change in electronegativity) < 0.5, the electrons are equally shared between

the two atoms resulting in a covalent bond.

If the ΔEN = 0.5 - 1.7, the electrons are not equally shared between the two atoms

resulting in a polar covalent bond.

If the ΔEN > 1.7, the electrons are not shared at all and it is an ionic bond.

In organic chemistry, we most commonly will deal with covalent bonds and polar covalent

bonds. Polar covalent bonds are of particular interest because they will help determine reactivity

later so it is important that you are able to pick out a polar covalent bond.

Example 1.1: Let’s look at the bond between carbon and oxygen:

C––O

Using the Table 1.1, we know that the electronegativity value for carbon is 2.5 and oxygen is 3.5.

Therefore, the ΔEN = 3.5-2.5= 1.0 and this is a polar covalent bond. Because oxygen is more

electronegative than carbon, more electron density is around the oxygen atom.

Electronegativity And Polar Covalent Bonds Worksheet With Answers