West Lothian Council
1
Atomic numbers
Note:
You already know that elements are made up of tiny particles
called atoms. The atoms of different elements are not the
same. For example, iron atoms are a different size and weight
from gold atoms.
Every element has been given a special number called the
atomic number. The atomic number can be found on a periodic
table for example on pages 1 and 8 of the data book.
Look up a data book page 8. You can see from the key what
each piece of information means.
key
Atomic number
Name of element
symbol
4
Beryllium
Be
You can see from the key that the element called berylllium has
an atomic number of 4.
Look up the box for phosphorus and you will see that it has an
atomic number of 15.
key
Atomic number
Name of element
symbol
15
Phosphorus
P
Write a heading and try the work below.
1. The tiny particles that elements are made from are called
a_____ .
2
2. Iron atoms are n___ the same as gold atoms. This is because
they have a different s________ and w__________ .
3. The page in the data book you look at to find the atomic
number for an element is page ____ .
4. Using page 8 of the data book complete the tables below and
fill them in with 20 elements of your choice.
Element
name
atomic
number
Element
name
atomic
number
Ask your teacher if your should do the sheet called “data book
exercise”.
3
Molecules and bonds
Note
Some substances are made up of molecules. A molecule is a
group of atoms that are joined together. The join between the
atoms is a kind of chemical glue called a bond.
A molecule of hydrogen would look like:
H
atom
H
bond
atom
A molecule of water would look like:
O
H
H
The bond between the atoms are very strong.
Write a heading and try the work below.
1. A molecule is a g______ of a______ joined together.
2. A bond is the j_____ between a________.
3. The bonds between the atomsare weak/strong.
4
Note
A beaker of water does not only contain one molecule it contains
billions of molecules. There is chemical glue holding the
different molecules together. This glue is also called bonds
but the bonds between molecules are only weak.
weak bond
O
atom
H
H
O
H
atom
H
O
atom
H
Strong bond
Continue your work by answering the questions below.
4. A beaker of water contains many molecules of water. The
chemical glue that holds them together is also called a
b____, but is w________ than the bond between atoms.
5. Complete the sentences below.
A molecule is a small group of a______ joined together
by b_______. The bonds between atoms are s_______
but the bonds between molecules are w______.
5
H
Substances and ions
Note
Not all substances are made from molecules. Some substances
are made from particles called ions. An ion is a charged
particle. An ion can be positively or negatively charged.
Substances that are made from ions are called ionic compounds
and contain both positive and negative ions joined together by
strong bonds.
Your teacher may show you a model of the ions in an ionic
compound.
ions
Strong bonds
Try the work below.
1. An ion is a c_________ p____________ .
2. An ion can either have a p___________ or n___________
charge on it.
3. The type of compounds made from ions are called i________
c_______________ .
4. The bonds between ions are strong/weak.
6
5. Using the ionic compound diagram on the previous page
choose two colours to colour in the positive and negative ions
before you stick it into your jotter.
Note
Substances can be solids, liquids or gases at room temperature.
In the next experiment you will find out a rule for the state of
ionic and molecular compounds.
6. Complete the table below and fill it in using display 4.
Substance
Molecular or
ionic
Solid, liquid
or gas
salt
water
oxygen
polystyrene
fertiliser
petrol
sulphur
baking soda
methane
epsom salts
7. Complete the rule below.
Ionic substances are always s________ at room
temperature but molecular substances can be s______,
l________ or g_____ at room temperature.
7
What about conducting electricity?
Note
You should already know from S1 and S2 that metals can
conduct electricity but what about whether ionic substances or
molecular substances conduct electricity. The aim of the next
experiment (1.39) is to find out if ionic substances or
molecular substances can conduct electricity.
The experiment we will use will be set up as shown in the
diagram below.
power
pack
4V AC
leads
A
ammeter
carbon
electrodes
substance being
tested
Try the work below.
1. The aim of the experiment is to find out if
______________________________________________
______________________________________________
2. What do you think will happen ______________________________________________
______________________________________________
______________________________________________
8
Carry out the experiment by going to each station and
connecting up the circuit and complete the table below:
Compound
Ionic/Molecular
Conducts electricity
(Y/N)
3. Now write a conclusion (what did you find out about the ionic
and molecular substances?)
______________________________________________
______________________________________________
______________________________________________
9
What about melting and boiling?
Note
Ionic and molecular substances are not only different in
conduction of electricity, they are also different in how they
melt or boil. The stronger the bonds in a substance, the
more heat is needed to make the substance melt.
Try the work below.
1. John has two chemicals labelled A and B. He knows that the
bonds in substance A are stronger than the bonds in
substance B. The chemical he will need to heat up more to
make it melt is ____ .
2. Complete the table below and complete it using the melting
and boiling point chart.
Name of
substance
Phenol
molecular
or ionic?
melting point boiling point
in C
in C
Calcium oxide
Naphthalene
Sodium bromide
3. The type of substance which always has high melting points
and boiling points is ionic/molecular.
4. Collect and complete the types of substances summary
sheet and stick it into your jotter.
10
Molecules and formulae
Note
You have now looked at molecular and ionic substances and the
last section of this booklet is about molecules and formula.
A formula is just a short way to show how many atoms are
present in a molecule. There are two rules that we need to
remember about writing formula:

Numbers always go after the symbols

We do not write the number one
Look at the molecule that is shown below.
H
H
H
C
C
H
H
O
H
This molecule has two carbon atoms, six hydrogen atoms and
one oxygen atom so it will have the formula:
C2H6O
All that we have done is counted the atoms and put in numbers
after the symbols.
11
Write a heading and try the work below
1. The two rules for writing formula are
°_____________________________________________
°_____________________________________________
2. The molecule that is show on page 11 has the formula C2H6O
because it contains _ carbons atoms. _ hydrogen atoms and _
oxygen atom.
3. Use a data book to complete the table below.
Colour of atom
Black
White
Red
Green
Yellow
Blue
element name
Carbon
Hydrogen
Oxygen
Chlorine
Sulphur
nitrogen
element symbol
C
4. Now look at the molecules that your teacher has put around
the classroom and for each one use a blank page to:
 Draw it
 Colour it in
 Work out its formula.
5. The molecules which show elements are
_______________________________________________
_______________________________________________
7. The molecules which have the same formula but a different
shape are
_______________________________________________
_______________________________________________
12
8. Collect a model kit and build five of your own molecules. The
rules are that you must use the grey bonds and make sure all of
the holes on the atoms are full. For each one draw it colour it
in and write it’s formula.
Your teacher may now ask you to do experiment 1.37. Follow
the instructions on the card and present your in the table below
Name Of Molecule
Chemical Formula
13
Compound names revisited
Note
You already know that the name of a chemical tells us about the
elements that are present. If the name ends in ide the
chemical contains two elements. The first part of the name
tells us one of the elements. The second part of the name gives
us a clue to the name of the second element.
eg sodium chloride contains the elements sodium and chlorine
(we need to check a data book for the full name of the second
element).
eg magnesium oxide contains the elements magnesium and
oxygen.
Write a heading then copy and complete the sentences below
to make sure you understand how to do this before you
start the next page.
Magnesium chloride contains the elements ______________
and __________.
Sodium oxide contains the elements ______________ and
______________.
Potassium chloride contains the elements ____________ and
_____________.
Barium oxide contains the elements ___________ and
____________.
Nitrogen hydride contains the elements ___________ and
_____________.
Carbon sulphide contains the elements ____________ and
_____________.
14
Names and prefixes
Note
The name of an object sometimes tells us about the object. For
example a tricycle has three wheels; an octopus has eight legs.
a triangle has
3 sides
a pentagon has
5 sides
The little bit that has gone at the beginning of the word is
called a prefix. Prefixes have different meanings.
prefix
meaning
mono
1
di
2
tri
3
tetra
4
penta
5
hex
6
hept
7
oct
8
The prefix tells us more about the chemical but does not
change the elements that are in it. For example carbon
tetrachloride is the same as carbon chloride so it will still
contain carbon and chlorine; carbon dioxide will still contain
carbon and oxygen.
Write a heading and try the work below.
1. You know that a tricycle has three wheels because it begins
with the prefix t___ .
2. The word octopus tell you that the animal has __ legs.
3. Using the above table complete the sentences below
Sulphur dioxide contains ___________ and __________.
Sulphur trioxide contains _________ and ____________.
Carbon monoxide contains ____________ and ___________.
Nitrogen
dioxide
contains
andoften
____________.
If we know
the name
of a ___________
substance we can
work out its
Phosphorus
pentachloride
___________
and _______.
formula even
if we cannot contains
see the atoms
to count them.
Silicon tetraflouride contains ____________ and __________.
15
Formula and prefixes
Note
Sometimes we can work out the formula of a molecule even if
we cannot see the molecule to count the atoms. We can do this
if the name has a prefix in it.
Carbon tetrachloride contains carbon and chlorine but tetra
means four so this tells us that there are four chlorine atoms.
There is not a prefix infront of the carbon part of the name so
this means that there is only one carbon atom.
The symbol for carbon is C
and the symbol for chlorine is
chlorine
Cl. The
carbon
The formula for this molecule will be
CCl4
You might have heard of a poisonous gas called called carbon
monoxide. The diagram below shows you how you can use the
name to work out the formula of this gas.
Carbon monoxide
This tells us the
molecule has a
carbon atom in it.
So the formula will be
This tells us
there is one
oxygen
This tells us the
molecule has
oxygen in it.
CO (remember we don’t write one’s in
chemistry).
16
Another example is shown below
Carbon dioxide
This tells us the
molecule has a
carbon atom in it.
So the formula will be
This tells us
there are
two oxygen
atoms.
This tells us the
molecule has
oxygen in it.
CO2
Complete the example below
Nitrogen monoxide
This tells us the
molecule has a
n_________
atom in it.
This tells us
there is ___
o_________
atom.
17
This tells us the
molecule has
o____________
in it.
1. Copy and complete the table below
name
carbon dioxide
elements
present
carbon and
oxygen
formula
carbon and
chlorine
nitrogen and
oxygen
CCl4
CO2
carbon monoxide
sulphur dioxide
sulphur monochloride
carbon tetrafluoride
Phosphorus trihydride
Uranium hexafluoride
diphosphorus trioxide
dinitrogen oxide
Diphosphorus pentoxide
18
NO2
19