Chemistry Reference
In-Depth Information
4. Lewis Structures
Topic
Lewis structures can be used to predict bonding capabilities of molecules.
Introduction
An atom has a tiny but dense nucleus that is composed of positively
charged protons and neutral neutrons. The nucleus is surrounded by
negatively charged electrons that orbit in paths known as
orbitals
. Atoms
are stable when their outermost orbitals are full of electrons. For all
elements other than hydrogen and helium (which have only one and two
electrons respectively), the outer shell is considered to be full when it
contains eight electrons, an
octet
. These outer shell electrons are known
as
valence electrons
. A Lewis dot structure, which is a diagram that
represents an atom, shows the valence electrons. In this type of diagram,
electrons are represented by dots that surround the element symbol. Dots
are positioned on each side of the symbol (top, bottom, left, and right).
Figure 1 shows Lewis dot structures for several elements.
1
2
13
14
15
16
17
18
H
He
Li
Be
B
C
N
O
F
Ne
Na
Mg
All
Si
P
S
CI
Ar
K
Ca
Se
Br
Kr
Rb
Sr
Te
I
Xe
Cs
Ba
Figure 1
Lewis dot structures for elements in groups 1 and 2
and 13 through 18 of the periodic table.
