Ionic Bonding
Mr. Van Brunner
The Octet Rule
• Atoms bond to achieve the electron
configuration of its nearest noble gas
• The resulting atoms become isoelectronic
– same number and distribution of electrons
as its nearest noble gas
Al
13 p+
14 n°
Ionic Bonding
• A metal and a non metal usually combine in an
ionic bond
•The metal loses one or more
electrons to become
isoelectronic with its nearest
noble gas, forming a positive
ion
Na
+
Low EN
Isoelectronic with Ne
‘Full octet’
•The non metal gains one or
more electrons to become
isoelectronic with its nearest
noble gas, forming a negative
ion
Cl-
high EN
Isoelectronic with Ar
‘Full octet’
Ionic Bonding
• Each ion is attracted to and surrounded by oppositely
charged ions and this strong force of attraction holds the ions
together
• The stable aggregate formed is called an ionic crystal
• The chemical formula for an ionic compound is referred to as
a ‘formula unit’ – as the compound does not exist in
isolation
• Lets explore this a little more on the next few slides…
NaCl does not exist as
a single unit like a molecule.
Like any ionic compound,
sodium chloride exists as a crystal:
The formula unit for sodium chloride is NaCl.
However, if we look inside the crystal,
+
the Na and Cl ions are each bonded
to six oppositely charged neighbors:
Let’s shrink
the ions so
we can take
a peek inside
Let’s shrink
the ions so
we can take
a peek inside
We’ll take a
look at this
Cl- ion.
How many
Na+ ions is
the Cl- close
enough to
bond with?
We’ll start
again
from the
head-on view
We’ll start
again
from the
head-on view
And,
how many
Cl- ions is
each Na+ ion
bonded to?
Because each Na+ is bonded to more than one Cl- ion,
and each Cl- is bonded to more than one Na+ ion, then
all the ions in the whole crystal are
part of one single bonded unit,
and the crystal below would be Na32Cl32.
This is impractical, given the enormous numbers
of ions in a crystal large enough to see with our eyes.
So, only the ratio of ions is given (its empirical formula),
which is called a formula
unit.
NaCl is the formula unit for
the sodium chloride crystal.
NaCl is the smallest whole number
ratio of sodium and chloride ions
in the crystal.
This is impractical, given the enormous numbers
of ions in a crystal large enough to see with our eyes.
So, only the ratio of ions is given (its empirical formula),
which is called a formula
unit.
NaCl is the formula unit for
the sodium chloride crystal.
NaCl is the smallest whole number
ratio of sodium and chloride ions
in the crystal.
Lewis Symbols (Electron Dot Diagrams)
The “kernel” of the atom (nucleus
and inner electrons) is represented
by a symbol
Cl
Lewis Symbols (Electron Dot Diagrams)
The “kernel” of the atom (nucleus
and inner electrons) is represented
by a symbol
Cl
valence electrons
are represented by
dots
Lewis Symbols (Electron Dot Diagrams)
•A symbol has
four sides and the
dots are
distributed
around these
sides
Cl
valence electrons
are represented by
dots
Lewis Symbols (Electron Dot Diagrams)
•Valence electrons
are placed
initially as single
dots on each side
of the symbol…
Cl
Lewis Symbols (Electron Dot Diagrams)
•Valence electrons
are placed
initially as single
dots on each side
of the symbol…
Cl
…and then are
paired as
necessary
Lewis Symbols (Electron Dot Diagrams)
•Valence electrons
are placed
initially as single
dots on each side
of the symbol…
Cl
…and then are
paired as
necessary
No more than two
dots can be
paired on one
side of the
symbol!
In an IONIC bond,
electrons are lost or gained,
resulting in the formation of IONS
in ionic compounds.
K
F
K
F
K
F
K
F
K
F
K
F
K
F
K
+
_
F
K
+
_
F
The compound potassium fluoride
consists of potassium (K+) ions
and fluoride (F ) ions
K
+
_
F
The ionic bond is the attraction
between the positive K+ ion
-
and the negative F ion
Let’s practice drawing Lewis dot
diagrams for Ionic
Compounds!!