1. No category

Chemistry
(14 - 16)
Chemical Bonding
(Ionic)
© SSER Ltd.
Ionic Compounds
Ionic compounds are made up of giant structures between metals
and non-metals.
They are usually hard crystalline solids with high melting points,
e.g. CsCl has a melting point of 646 ºC.
Ionic Compounds
The crystalline shape reflects
the internal symmetry in
which millions of particles are
arranged in a regular lattice
structure.
The different particles have
opposite charges and are
called ions.
The ions exert strong electrostatic attractions within the lattice this attraction is called IONIC BONDING.
The ions are formed when the elements react with one another.
The elements react in an attempt to become more stable.
The Formation of Ions
Ions are formed when one atom pulls the electron(s) completely
away from another atom, giving both atoms a full outer shell of
electrons. This gives a much more stable structure.
The Formation of Ions
Ions are formed when one atom pulls the electron(s) completely
away from another atom, giving both atoms a full outer shell of
electrons. This gives a much more stable structure.
The Formation of Ions
I
II
III
IV
V
VI
VII
0
Li
Na
K
Rb
Cs
Fr
All Group 1 elements readily lose one
electron to complete their outer electron
The ion has
shell, giving a noble gas electronic
a 1+ charge.
configuration.
As a result of the ease with which all the Group 1 elements lose
an electron, they have similar chemical properties, i.e.
react with Halogens forming ionic compounds in which the
Group 1 ion has a single positive charge.
The Formation of Ions
I
II
III
IV
V
VI
VII
0
F
Cl
Br
I
At
All Group 7 elements readily accept one
electron to complete their outer electron
The ion has a
shell, giving a noble gas electronic
1- charge.
configuration.
As a result of the ease with which all the Group 7 elements
accept an extra electron, they have similar chemical properties,
i.e. react with alkali metals forming ionic compounds in which
the Group 7 ion has a single negative charge.
The Formation of Sodium Chloride
The sodium and chlorine atoms need full outer shells of electrons
to achieve stability.
The sodium atom has one electron in its outer shell.
The chlorine atom has one space in its outer shell.
The Formation of Sodium Chloride
Stability is achieved by the donation of an electron from the
sodium atom to the chlorine atom, to form sodium chloride.
This gives both ions a noble gas electronic configuration.
The Formation of Sodium Chloride
+
-
The sodium atom takes on an electronic configuration of 2,8
and becomes a positively charged sodium ion (Na+).
The chlorine atom takes on an electronic configuration of
2,8,8 and becomes a negatively charged chloride ion (Cl-).
The Formation of Sodium Chloride
The two ions strongly attract one another as a result of their
opposite electrostatic charges.
A stable, ionic compound, sodium chloride (NaCl) is the product.
The Formation of Sodium Chloride
The two ions can also be represented as follows:
+
_
The Formation of Sodium Chloride - Summary
Ions are formed when the chlorine atom pulls a single electron
completely away from a sodium atom, giving both atoms a full
outer shell of electrons. This gives a much more stable structure.
Start the animation to see how ionic sodium chloride is formed...
The Formation of Sodium Chloride - Summary
Ions are formed when the chlorine atom pulls a single electron
completely away from a sodium atom, giving both atoms a full
outer shell of electrons. This gives a much more stable structure.
Start the animation to see how ionic sodium chloride is formed...
The Formation of Sodium Chloride
When sodium and chlorine gas react together, a very stable ionic
compound, sodium chloride (NaCl) is the product.
The Formation of Sodium Chloride
When sodium and chlorine gas react together, a very stable ionic
compound, sodium chloride (NaCl) is the product.
2Na + Cl2 
Surface of the sodium
What is needed to
2NaCl
balance the equation?
The Formation of Sodium Chloride
The diagram shows
how sodium ions and
chloride ions pack
together in a single
plane of a sodium
chloride crystal.
The forces of attraction
between the ions act in
all directions within the
crystal structure.
Cl
-
Na+
Cl
-
Na+
Na+
Cl
-
Na+
Cl
-
Na+
-
Na+
Na+
-
Cl
Cl
Cl
Na+
Cl
-
-
The Formation of Sodium Chloride
This is a 3-D view of a ball and stick model of a sodium chloride
lattice.
Key
sodium ion
chloride ion
Sodium Chloride - Ionic Crystal Lattice
As more ions are added to the structure, the lattice takes shape.
Each ion has six nearest neighbour ions of opposite charge.
Sodium Chloride - Ionic Crystal Lattice
This image shows a corner of the giant ionic lattice of NaCl.
Sodium Chloride – Ionic Crystal Lattice
Crystals of sea salt (sodium chloride) magnified one hundred times.
Notice the cubic shape of the crystal in the centre of the photograph.
The cubic shape of the crystal is directly due to the cubic lattice.
The Formation of Magnesium Chloride
Magnesium and chlorine also form an ionic compound called
magnesium chloride (MgCl2).
The magnesium atom has two spare electrons in its outer shell.
Stability is achieved by the donation of an electron from the
magnesium atom to each of the two chlorine atoms, giving the
three ions a noble gas electronic configuration.
The Formation of Magnesium Chloride
Both chlorine atoms take up an electronic configuration of
2,8,8 and become negatively charged chloride ions.
The magnesium atom now has an electronic configuration of
2,8 and becomes a dipositively charged magnesium ion.
The Formation of Magnesium Chloride
-
2+
-
The ions attract one another as a result of their opposite
electrostatic charges. An ionic compound, magnesium chloride,
Mg2+Cl-2 is the product.
Therefore the formula of magnesium chloride is MgCl2.
The Formation of Magnesium Chloride
When magnesium and chlorine react together a very stable
ionic compound, magnesium chloride (MgCl2) is the product.
The Formation of Magnesium Chloride
When magnesium and chlorine react together a very stable
ionic compound, magnesium chloride (MgCl2) is the product.
Surface of the magnesium
Mg + Cl2  MgCl2
The Formation of Calcium Chloride
As calcium is in the same group of the Periodic Table as
magnesium, calcium chloride is formed in a similar way to
magnesium chloride.
Stability is achieved by the donation of an electron from the
calcium atom to each of the two chlorine atoms, giving the three
ions a noble gas electronic configuration.
The Formation of Calcium Chloride
The ions attract one another as a result of their opposite
electrostatic charges. An ionic compound, calcium chloride, Ca2+Cl2 is the product.
Therefore the formula of calcium chloride is CaCl2.
Metal Lattice – Free Electrons
A more detailed model of a metal lattice describes the lattice as
having an outer layer of mobile electrons which can jump from
atom to atom.
This arrangement has been described as ‘metallic meat balls
in a fluid electronic soup’. Our model of the lattice can now
to this...
be changed from this...
Metal Lattice
The electron soup is a result of the delocalisation of the free
electrons in the outer shells of each atom.
These delocalised electrons enable metals to conduct electricity.
Metal Lattice
The electron soup is a result of the delocalisation of the free
electrons in the outer shells of each atom.
These delocalised electrons enable metals to conduct electricity.
End of Show
Copyright © 2007 SSER Ltd. and its licensors.
All rights reserved.
All graphics are for viewing purposes only.