Transcript Bonding

Bonding
Chemistry revision
There are two types of
bonding you need to be
familiar with…
1. Covalent bonding
2. Ionic bonding
You will be re-visiting…
The structure of the atom.
Why atoms want to lose or gain electrons.
Which type of materials use covalent or
ionic bonding.
The properties that covalent and ionic
bonding give to the material.
You need to be able to…
Name the components of an atom.
Understand how many electrons are in each
orbital.
Describe the charge on each sub atomic
particle.
Understand what an isotope is.
To draw dot and cross diagrams.
To draw ionic formula diagrams.
To name compounds which use these types
of bonding
The atom
Atoms contain three sub-atomic particles called
protons, neutrons and electrons.
The protons and neutrons are found in the nucleus
at the centre of the atom, and the electrons are
arranged in shells around the nucleus.
The charge in an atom
• Atomic heaven is to be neutral!
• Atoms will share or steal electrons so they
can to obtain the structure of the Group 0
or Noble elements.
• This group reacts with very little at all!
• By sharing or stealing electrons the atoms
bond to become compounds and therefore
neutral!
Particle
Charge Relative Mass
Protons
+1
1
• There are two properties of
sub-atomic particles that are
especially important:
Neutrons
0
1
Mass
Electrical charge
Electrons
-1
0.0005
So now we look at the Periodic Table…
Here is the
Atomic Number = the number
element
of protons in the nucleus.It is
Carbon
the smaller number in the box.
12
C
6
Atomic Mass = the number of
protons and neutrons in the
nucleus.It is the larger number in the
box.
From these two numbers we can work out the
number of electrons this element should have.
Carbon can also be an isotope
Isotopes have the same number of
protons but a different number of
neutrons. So isotopes have the same
atomic number but a different atomic
mass.
12 C or 14 C
6
6
Other famous isotopes are uranium
and radium
Where are the electrons?
The electrons are located in orbitals
or shells around the nucleus.
The innermost orbital will take up to
two electrons only.
The next three orbitals will take a
maximum of eight electrons each.
Covalent Bonding
•
•
•
Covalent compounds are formed when non-metal
atoms react together.
As these atoms come near their outer electrons are
attracted to the nucleus of both atoms and become
shared by the atoms.
The shared electrons count towards the shells of
both atoms and therefore help fill up incomplete
electron shells.
Boardworks –
Covalent Bonding
Examples of covalent bonding
Simple covalent bonds:
Water H2O
Ammonia NH3
Methane CH4
Oxygen O2
Giant covalent structures:
Graphite
Diamond
Properties of covalent compounds
Small numbers of atoms in the
molecules.
Low melting and boiling points.
Most are gases or liquids at room
temperature.
They do not conduct electricity.
They tend to be insoluble in water.
Ionic bonding
Most ionic compounds contain a metal and a
non-metal.
When metals react they lose outer shell
electrons to leave a full electron shell.
This produces a charged atom (ion)
with a + charge.
When non-metals react with a metal they
gain electrons to achieve a full electron
shell.
Ions and electron structures
Metals lose electrons to form
positive(+) ions called cations.
Non-metals gain electrons to form
negative (–) ions called anions.
n+
n-
We know that the atoms lose or
gain electrons to achieve full
electron shells.
To understand more about how
ionic compounds form we must
look at what is happening to the
outer shell electrons.
© Boardworks Ltd 2003
Formation of Sodium Chloride- the overall process.
Sodium loses its
outer electron.
Chlorine gains it.
The result is
both end up with
full shells
Two oppositely
charged ions
are formed,
which attract.
Millions of such
pairs form a
giant lattice
Na
Na
Cl
Cl
© Boardworks Ltd 2003
Examples of ionic structures
Animation
of NaCL
Properties of ionic compounds
Atoms are held very strongly together.
The compound has a regular structure.
Ions form giant structures.
Very high melting and boiling points.
Soluble in water.
Conducts electricity when dissolved.
OK, have a go at this quiz and
check what you should know
This is the
structure
of Argon
It’s electronic
configuration
is written
2,8,8
Which group of
the Periodic
Table will it be
found in?