Chemistry Reference
In-Depth Information
Lewis dot diagrams can also be used to represent ionic compounds.
When dealing with ionic compounds, it is important to remember that the
individual atoms in the ionic compound complete their valence shells, by
gaining or losing electrons, before you put the Lewis dot diagram together.
For this reason, instead of showing elemental Lewis dot diagrams that seem
to interlock to form complete octets, we draw diagrams that show com-
plete octets that are next to each other. To make this even clearer, brack-
ets are sometimes drawn around the individual ions, to draw attention to
the fact that the ions are not sharing electrons.
Let's use the example of sodium chloride. Sodium, an alkali metal from
column 1, loses one electron to form an ion with a charge of +1. When
sodium loses that one valence electron, its inner energy level becomes its
complete octet, so we draw sodium with eight valence electrons and a charge
of +1. Chlorine begins with seven valence electrons but then steals an ad-
ditional electron (perhaps from the sodium atom) to form an ion with eight
valence electrons and a charge of -1. When we put these two ions together,
we get the Lewis dot diagram shown in Figure 4-3g.
Lewis Dot Notation for Sodium Chloride
-
+
Cl
Na
These ions don't share electrons, and their Lewis dot diagrams don't overlap.
They are held together by the nature of their opposite charges.
Figure 4-3g
Lesson 4- 3 Review
Use the following Lewis dot notations to answer questions 1-4.
2+
A.
B.
C.
D.
Li
Ba
Ar
Br
1.
Which shows a neutral element that is chemically stable?
2.
Which shows an atom that has lost two electrons?
3.
Which element could complete its octet by forming a single covalent
bond?
4.
Which neutral element is most likely to form a positive ion, with a
charge of +1?
