Btec C2 – Chemical Bonding (ACT)
Lesson 1 – Chemical Bonding
Chemical Bonding
• Demo…
– Hydrogen balloon
– Methane Balloon
– Carbon dioxide balloon
– Hydrogen burning in oxygen
• Questions…
– What can you tell Mr C about the density of hydrogen and
carbon dioxide?
– What are the boiling points of…
• Water
• Hydrogen
• Carbon dioxide
• Methane
Experiment…
• Measure melting point of
– Salol
– Solder (tin/lead)
– Salt
• Use mercury of IR thermometer
• Questions…
– What are the melting points of
the compounds above?
– Which compound has the
strongest bonds between atoms?
– What can you tell Mr C about the
strength of bonds between,
• A pair of CO2 atoms
• A pair of methane atoms
Task…
• You will be investigating chemical bonding…
• Draw a series of diagrams to show how a chlorine atom bonds
with a sodium atom,
• You must include…
– Atomic structures (showing the electrons) of sodium and
chlorine atoms before they bond
– Atomic structures (showing the electrons) of sodium and
chlorine atoms after they bond
– An indication of where electrons move during the bonding
process.
• Use Longman foundation 2, page 148-149 to help.
• Use A3 paper as groups, then complete a neat version
individually, after Mr. C has checked your work.
Extension:
• Draw diagrams to show how (a) Lithium Fluoride, and, (b)
Lithium oxide bonds
Ionic Bonding
Sodium has 1 electron in
its outer shell
Chlorine has 7 electrons in
its outer shell, or you
could say that it has one
space in its outer shell.
They both want full outer
shells, so,
Sodium will loose an
electron and gives it to
chlorine…
So…
Sodium has a positive
charge
Chlorine has a negative
charge
They are attracted
together
Ionic bonding
This is where a metal bonds with a non-metal (usually). Instead of sharing the
electrons one of the atoms “_____” one or more electrons to the other. For
example, consider sodium and chlorine:
Na
Sodium has 1 electron on its outer shell
and chlorine has 7, so if sodium gives its
electron to chlorine they both have a ___
outer shell and are ______.
+
A _______
charged
sodium ion
Na
Cl
Cl
A _________
charged chloride
ion
As opposed to covalent bonds, ionic bonds form strong forces of
attraction between different ions due to their opposite ______,
causing GIANT IONIC STRUCTURES to form (e.g sodium
chloride) with ______ melting and boiling points:
Lesson 2 – Giant Structures
• What is the melting point of sodium
chloride?
• What is the name of the bond
between a sodium atom and a
chlorine atom?
• Ionic bonds (transfer of electrons)
• Strong,
• This means that the melting point is
high as you need a lot of energy to
break the strong bonds between
atoms.
MP ~ 800˚C
Task…
• Make your own sodium chloride
structure…
1. Colour 8 cubes green, these are the
chlorine atoms
2. Colour 8 cubes grey, these are the
sodium atoms
3. Using the art straws and sellotape,
make a model of the structure of
sodium chloride
MP ~ 800˚C
Covalent Bonding
• So far...
Ionic
Bond
Metal
NaCl
and Nonmetal
Electron
transfer
Covalent
Bond
NonH2
metal
and Nonmetal
Sharing
Strong
electrons bond
Individual
molecules
Metal
Bond
Metal
and
Metal
Free
Strong
Electrons
Giant
random
structure
Fe
Strong
Makes
giant
structure
Covalent bonding
Consider an atom of hydrogen:
Notice that hydrogen has just __ electron in its outer shell. A
full (inner) shell would have __ electrons, so two hydrogen
atoms get together and “_____” their electrons:
Now they both have a ____ outer shell and are more
_____. The formula for this molecule is H2.
When two or more atoms bond by sharing electrons we call
it ____________ BONDING. This type of bonding normally
occurs between _______ atoms. It causes the atoms in a
molecule to be held together very strongly but there are
____ forces between individual molecules. This is why
covalently-bonded molecules have low melting and boiling
points (i.e. they are usually ____ or ______).
Words – gas, covalent, non-metal, 1, 2, liquid, share, full, weak, stable
The periodic table
.5
Covalent Bonding –
Sharing Electrons
• Hydrogen atoms have one electron
in their outer shell
• But they want two..!
Covalent Bonding –
Sharing Electrons
• Hydrogen atoms have one electron in
their outer shell
• But they want two..!
• If they go round as a pair they can
share electrons, so they both have a
full outer shell
• This sharing of electrons is known as
Covalent bonding
Covalent Bonding 2
• In a water molecule the hydrogen and oxygen atoms are
covalently bonded e.g.
• electrons from the
oxygen atom
x electrons from the
hydrogen atom
Dot and cross diagrams
Water, H2O:
Step 1: Draw the atoms with
their outer shell:
Step 2: Put the atoms together and
check they all have a full outer shell:
H
O
H
O
H
H
Oxygen, O2:
O
O
O
O
-
+
+
Metallic Bonding
• Metals form giant structures in
which electrons in the outer
shells of the metal atoms are
free to move.
• The metallic bond is the force of
attraction between these free
electrons and metal ions.
• Metallic bonds are strong, so
metals can maintain a regular
structure and usually have high
melting and boiling points.
• Metals are good conductors of
electricity and heat, because
the free electrons carry a
charge or heat energy through
the metal. The free electrons
allow metal atoms to slide over
each other, so metals are
flexible.
• Longman FND 2, page 146-147
Questions – Summary of Chemical
Bonding
1. Match the correct
type of bonding to
the elements that
are joined...
2. Draw a diagram to
show how the
atoms are bonded
in each type of
bond.
Show the electron
arrangement.
3. Summary Q from
Longman 2...
(pages...146, 148
& 154)
Element 1
Element 2
Type of
bonding
Magnesium Chlorine
Metal
Carbon
Hydrogen
Ionic
Iron
Iron
Covalent
Experiment...
Investigate the solubility of
– group 1 salts,
– covalent and
– metallic compounds
in water and alcohol. Worksheet: ‘Solubility’
• Watch animation, complete task sheet on different types
of bonding
Questions to summarise Covalent /
ionic and metallic bonds
Sodium Chloride….
Dissolved in water, sodium chloride will
split up and form the following ions…
1.Na+
2.ClFrom salt
3.H+
4.OH-
From water
Na+ or H+ ion
Cl- or OH- ion
• The positive ions (Na+ and H+) will, be attracted to the negative
electrode (metal ions are usually positive)
• The negative ions (Cl- and OH-) will be attracted to the positive
electrode (non- metal ions are usually negative)
Questions on Electrolysis
• Foundation Science 1
• Draw a series of diagram to show what happens to the
atoms when sodium chloride dissolves in water, then
undergoes electrolysis
Assessment
Grading criteria P2
• Investigate and describe ionic,
covalent and metallic bonds.
Grading criteria M2
• Investigate and explain the
properties of substance with
ionic, covalent and metallic
bonds.
Grading criteria D2
• Explain bonding in terms of
stability… a means to achieving
a full outer shell either by
transferring or sharing
electrons.
What you need to do…
Scenario….
• You work in a research laboratory at the University of
Plymouth.
• The Environment Agency has approached you with four
chemical samples that have been found near the play area at
‘Freedom Field Park’.
• They have asked you to identify the type of substance as either
ionic, covalent or metallic and given them an outline of the
type of properties these substance will have.
• You will carry out a practical assignment to identify the four
unknown samples and you will produce a letter from the
University to the Environment Agency in London.
• This letter will include your identification of the four samples
and justify your reasons (P2) an explanation of the properties
of the samples (M2) and detailed explanation of the structure
of any covalent or ionic substances found (D2)
Exp
Test the four samples and identify them as either ionic, covalent
or metallic. Show you results in a table. Diagram.
Justify your identification of each sample with data from your
tests.
146,148
154,
135,
139,
143
Write you letter from the University to the Environment Agency
Describe what your results tell you about the four samples.
Include your results and what you results show, with justification.
Use diagrams to explain how the atoms bond together in ionic,
covalent and
metallic
bonding. FND book 2
Numbers
in black
– Longman
150, 142 Explain, with a diagram, in the letter, how ionic substances
Numbers
insolution.
Blue – AQA Science book
dissolve in
148, 139 Explain, in the letter, why ionic substances have a higher melting
and boiling point compared to simple covalent.
146, 143 Explain, in the letter, why metals and dissolved ionic substances
conduct electricity.
Int, 138
Explain, in the letter, why graphite is an unusual giant covalent
and how it is able to conduct electricity.
148, 139 Use dot and cross diagrams in the letter to explain how the ionic
substances achieve stability through transferring electrons.
154, 136 Use dot and cross diagrams in the letter to explain how the
covalent substances achieve stability through sharing
electrons.
Exp

Test the four samples and identify them as either ionic, covalent
or metallic. Show you results in a table. Diagram.
 Justify your identification of each sample with data from your
tests.
146,148
154,
135,
139,
143




Write you letter from the University to the Environment Agency
Describe what your results tell you about the four samples.
Include your results and what you results show, with justification.
Use diagrams to explain how the atoms bond together in ionic,
covalent and metallic bonding.
150, 142  Explain, with a diagram, in the letter, how ionic substances
dissolve in solution.
148, 139  Explain, in the letter, why ionic substances have a higher melting
and boiling point compared to simple covalent.
146, 143  Explain, in the letter, why metals and dissolved ionic substances
conduct electricity.
Int, 138
 Explain, in the letter, why graphite is an unusual giant covalent
and how it is able to conduct electricity.
148, 139  Use dot and cross diagrams in the letter to explain how the ionic
substances achieve stability through transferring electrons.
154, 136  Use dot and cross diagrams in the letter to explain how the
covalent substances achieve stability through sharing electrons.