Chemistry Reference
In-Depth Information
electronegativity difference between the bonding atoms is moderate, then
a polar covalent bond is formed. By “polar” we mean that it has a positive
end and a negative end, akin to the poles on a bar magnet.
In this topic, we will consider a bond that is formed between two atoms
that have an electronegativity difference of 0.0-0.3 to be a non-polar cova-
lent bond. If the electronegativity difference between the bonding elements
is 0.4-1.7, we will consider the bond formed to be a polar covalent bond.
When the electronegativity difference between the two elements is greater
than 1.7, we will call the formed bond an ionic bond.
Major Types of Bonds Between Atoms
Ionic bond
A bond formed between a negative ion
(anion) and a positive ion (cation).
Covalent bond
A bond formed when atoms share one or
more pairs of electrons.
Non-polar covalent bond
A bond formed when atoms share one or
more pairs of electrons relatively equally.
Polar covalent bond
A bond formed when atoms share one or
more pairs of electrons but one atom at-
tracts the electrons more strongly, result-
ing in unequal sharing.
Let's try a few examples of determining the type of bond that forms
between two elements.
Example 1
Determine the types of bonds that form between the following pairs
of elements.
A. KCl B. H
2
O C. HCl D. O
2
All we need to do is look up, and subtract, the electronegativities (E.N.)
of the bonding elements. We ignore any subscripts, such as the subscript of
“2” found in the H
2
O.
A. From Figure 4-1a, we find:
E.N. of K = 0.8
E.N. of Cl = 3.2
Difference in E.N. = 2.4 (3.2 - 0.8 = 2.4).
Because 2.4 is greater than 1.7, this bond is ionic.
