1. Topic 1.2 Atoms

2. Topic 2: Atoms
 Why study Atoms?
 Without a knowledge and understanding of what at
atom is and what it is made of how can a scientist
hope to understand or predict how something will
react and bond to make a new compound.
 Without this knowledge what is the purpose of
Chemistry (or indeed Biology or Physics)?
 Without this fundamental knowledge there can be
no understanding of Science.

3. Take a risk, it’s what scientists do!
 There is no wrong answer!
 Using what you know and understand so far draw
(and label if you can) what you think an atom looks
like. Put a box around it and write: “This is what I
believed an atom looked like on 11/8/2011”
 It will be interesting to look back in a few lessons to
see how close your understanding was to the
current understanding of what an atom looks like.
11/8/2011

4. The atom has taken a LONG time to work out
 In groups you are provided with the history of the
discovery of the atom.
 In your group you have to try to place this history
into the correct order, you will then have to re-draw
your idea of the atom based on this information.
 Divide the cards between the group, read them
carefully then discuss as a group and try to place
them in chronological order.

5. Time to take another risk
 Based on your new learning, draw a new labeled
diagram of what you think the atom looks like.
 This is an individual activity, it doesn’t matter what
the person next to you thinks!
 After you have finished your diagram, compare and
discuss with the rest of your group then on the
spare paper try to agree on a group model.

6. So which of these pictures is closest to the
truth?
A B
C D

7. So what does an atom look like?
 We’re still not exactly sure!
 Even with the most advanced technology that we
have they are too small to observe, an individual
atom is less than a 10th of a 1,000,000th of a
millimeter in diameter! Or 0.00000001mm, as in
10,000,000 of them side by side would just fill a
1mm gap on your ruler
 So they are really rather small, but if you think that
is small, just wait…

8. Recap time: What is an atom made of?
Name of particle Charge
Proton +1
Neutron 0
Electron -1

9. So what use are atoms?
 All substances are made of atoms.
 A substance that is made of only one type of atom
is called and element. Elements are shown in the
Periodic Table.
 Looking at the Periodic Table, can you identify
where the metals are and where the non-metals
are?

10.  In each element the number of electrons is equal to
the number of protons, the number of neutrons can
change.
 The atomic number is the number of protons an
atom has.
 The atomic ,ass number is the number of protons
plus the number of protons.

11. 55
Mn
Manganese
25

12. Element No of protons No of neutrons No of electrons
Hydrogen 1 1
Copper 29 35
Calcium 20 20
Sulfur 16
Potassium 19
Chlorine 18
Nickel 28
Magnesium 12
Carbon 6
Arsenic 42

13. Proton number = type of element
 All atoms of a particular element have the same
number of protons.
 Atoms of different elements have different number
of protons.
 What happens to the number of protons as you go
across the Periodic Table from left to right?

14. The number of neutrons
 What are isotopes?
 What makes them different?
 What keeps them the same?
 What makes them useful?
 What are some common examples and what are
their uses?

15. Relative atomic mass - Ar
 The relative atomic mass shown on the periodic
table is an average mass of all the isotopes of an
element compared (relative) to the mass of the 12C
isotope.
 Even the mass shown for C on the Periodic Table is
measured relative to the 12C isotope.
 At GCSE you do not have to calculate this!

16. Electrons
 Each atom has the same number of electrons as it
does protons.
 Protons have a positive charge, each proton has a
charge of +1
 Electrons have a negative charge, each electron has
a charge of -1
 The charges of the protons and the electrons cancel
each other out so that there is no overall charge on
an atom.

17. Locating the electrons
 The electrons orbit the nucleus of an atom in
energy levels (or shells).
 The electrons occupy the lowest available energy
levels (the ones nearest the nucleus) first.
 The position of the outermost electron dictates the
reactivity of an element.

18. Flame tests
 When heated by a Bunsen burner flame each
metallic element will ‘emit’ a specific colour of
visible light – this is called its atomic spectrum.
 Place a splint into a small sample of a salt and place
into the roaring flame of a Bunsen burner – record
the name of the salt and the colour of the flame it
produces.

19. Locating electrons
 The electrons orbit the nucleus of an atom in
energy levels (or shells).
The nucleus is at the center
The first energy level is small and can
only hold 2 electrons
The next two energy levels,
being further away and bigger
can hold up to 8 electrons each

20. Recap time: What are the masses of the
particles?
Name of particle Mass
Proton
Neutron
Electron