Atomic structure
Mrs Griffiths
Wellington School
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Atomic Structure
The structure of the atom
The Ancient Greeks used to believe that
everything was made up of very small particles. I
did some experiments in 1808 that proved this
and called these particles ATOMS:
Dalton
NEUTRON –
neutral, same
mass as
proton (“1”)
PROTON –
positive, same
mass as
neutron (“1”)
ELECTRON –
negative, mass
nearly nothing
The Atom
Nucleus
Shell or Orbit
Electron
The Atom Hydrogen
Proton
Electron
Hydrogen has one proton, one electron and NO neutrons
The Atom Helium
Proton
Electron
Neutron
Helium has two electrons, two protons and two neutrons
Mass andRelative
atomic
number
Mass
Relative Charge
Particle
Proton
Neutron
Electron
1
1
0
1
0
-1
MASS NUMBER = number of
protons + number of neutrons
SYMBOL
PROTON NUMBER = number of
protons (obviously)
The Atom Helium
Proton
Electron
Neutron
Helium has two electrons, two protons and two neutrons
The Atom Lithium
Protons
Neutrons
Electrons
The Atom Beryllium
Protons
Electrons
Neutrons
Beryllium has four electrons, four protons and five neutrons.
The Atom Boron
Protons
Neutrons
Boron has five electrons, five protons and six neutrons.
Electrons
The Atom Carbon
Protons
Neutrons
Carbon has six electrons, six protons and six neutrons.
Electrons
The Atom Nitrogen
Protons
Electrons
Neutrons
Nitrogen has seven electrons, seven protons and seven neutrons.
The Atom Oxygen
Protons
Electrons
Neutrons
Oxygen has eight electrons, eight protons and eight neutrons.
The Atom Fluorine
Protons
Electrons
Neutrons
Fluorine has nine electrons, nine protons and ten neutrons.
The Atom Neon
Protons
Neutrons
Neon has ten electrons, ten protons and ten neutrons.
Electrons
The Atom Sodium
Protons
Electrons
Neutrons
Sodium has eleven electrons, eleven protons and twelve neutrons.
How many protons, neutrons and electrons?
Periodic table
The periodic table arranges all the elements
in groups according to their properties.
Vertical
columns are
called GROUPS
Mendeleev
Horizontal rows are called PERIODS
The Periodic Table
Fact 1: Elements in the same group have the
same number of electrons in the outer shell (this
correspond to their group number)
H
He
Li
Be
B
C
N
O
F
Na
M
g
Al
Si
P
S
Cl Ar
K
Ca
Fe
Ni
C
u
Zn
Ag
Pt
E.g. all group 1 metals
have __ electron in
their outer shell
A
u
Ne
Br Kr
I
Xe
H
g
These elements have
__ electrons in their
outer shells
These elements
have __ electrons
in their outer shell
The Periodic Table
Fact 2: As you move down through the periods an
extra electron shell is added:
E.g. Lithium has 3
electronHin the
configuration 2,1
He
Li
Be
B
C
N
O
F
Na
M
g
Al
Si
P
S
Cl Ar
K
Ca
Sodium has 11
electrons inFethe Ni
configuration 2,8,1
Pt
Potassium has 19
electrons in the
configuration __,__,__
C
u
Zn
Ag
A
u
Br Kr
I
H
g
Ne
Xe
Fact 3: Most of the elements are metals:
The Periodic Table
H
These elements
are metals
He
Li
Be
B
C
N
O
F
Na
M
g
Al
Si
P
S
Cl Ar
K
Ca
Fe
Ni
C
u
Zn
Ag
Pt
A
u
This line divides
metals from nonmetals
Ne
Br Kr
I
Xe
H
g
These elements are
non-metals
Fact 4: (Most important) All of the elements in
the same group have similar PROPERTIES. This
is how I thought of the periodic table in the first
place. This is called PERIODICITY.
The Periodic Table
H
He
Li
Be
B
C
N
O
F
Na
M
g
Al
Si
P
S
Cl Ar
K
Ca
Fe
Ni
C
u
Zn
Br Kr
Ag 1 metals. They all:
I
E.g. consider the group
1) Are soft
Pt
A
u
H
g
2) Can be easily cut with a knife
3) React with water
Ne
Xe
Group 1 – The alkali metals
Li
Na
K
Rb
Cs
Fr
Group 1 – The alkali metals
Some facts…
1) These metals all have ___
electron in their outer shell
2) Reactivity increases as you go _______ the group. This is
because the electrons are further away from the _______
every time a _____ is added, so they are given up more easily.
3) They all react with water to form an alkali (hence their
name) and __________, e.g:
Potassium + water
2K(s)
+
2H2O(l)
potassium hydroxide + hydrogen
2KOH(aq)
+
Words – down, one, shell, hydrogen, nucleus
H2(g)
Group 0 – The Noble gases
He
Ne
Ar
Kr
Xe
Rn
Group 0 – The Noble gases
Some facts…
1) All of the noble gases have
a full outer shell, so they are
very _____________
2) They all have low melting and boiling points
3) They exist as single atoms rather then diatomic molecules
4) Helium is lighter then air and is used in balloons
and airships (as well as for talking in a silly voice)
5) Argon is used in light bulbs
(because it is so unreactive)
and argon , krypton and neon
are used in fancy lights
Group 7 – The halogens
F
Cl
Br
I
At
Group 7 – The Halogens
1) Reactivity DECREASES
as you go down the group
Decreasing
reactivity
Some facts…
(This is because the electrons are further away from the
nucleus and so any extra electrons aren’t attracted as much).
2) They exist as
diatomic molecules (so
that they both have a
full outer shell):
Cl
Cl
3) Because of this fluorine and chlorine are liquid at room
temperature and bromine is a gas
1) Halogen + metal:
The halogens – some reactions
+
+
Na
Cl
Halogen + metal
Cl
Na
ionic salt
2) Halogen + non-metal:
H
+
Cl
Halogen + non-metal
Cl
H
covalent molecule
-
How shells fill
• The first electron shell can only hold a
maximum of two electrons.
• The second electron shell can hold a
maximum of eight electrons.
• The third electron shell can also hold a
maximum of eight electrons.
• The fourth electron shell can also hold eight
electrons.
Consider an atom of Potassium:
Electron structure
Potassium has 19 electrons.
These are arranged in shells…
Nucleus
The inner shell has __ electrons
The next shell has __ electrons
The next shell has __ electrons
The next shell has the remaining __ electron
Electron structure
= 2,8,8,1
How the shells fill with electrons
Element
Shell 1
Shell 2
Shell 3
Shell 4
Hydrogen 1 electron 0 electron 0 electron 0 electron
H
Helium
He
2 electron 0 electron 0 electron 0 electron
How the shells fill with electrons
Element
Shell 1
Shell 2
Shell 3
Shell 4
Lithium
Li
2 electron 1 electron 0 electron 0 electron
Beryllium 2 electron 2 electron 0 electron 0 electron
Be
How the shells fill with electrons
Element
Shell 1
Shell 2
Shell 3
Shell 4
Boron
B
2 electron 3 electron 0 electron 0 electron
Carbon
C
2 electron 4 electron 0 electron 0 electron
How the shells fill with electrons
Element
Shell 1
Shell 2
Shell 3
Shell 4
Nitrogen
N
2 electron 5 electron 0 electron 0 electron
Oxygen
O
2 electron 6 electron 0 electron 0 electron
How the shells fill with electrons
Element
Shell 1
Shell 2
Shell 3
Shell 4
Fluorine
F
2 electron 7 electron 0 electron 0 electron
Neon
Ne
2 electron 8 electron 0 electron 0 electron
How the shells fill with electrons
Element
Shell 1
Sodium
Na
Shell 2
Shell 3
Shell 4
2 electron 8 electron
1 electron
0 electron
Magnesium 2 electron 8 electron
Mg
2 electron
0 electron
How the shells fill with electrons
Element
Shell 1
Shell 2
Shell 3
Shell 4
Aluminium 2 electron 8 electron
Al
3 electron
0 electron
Silicon
Si
4 electron
0 electron
2 electron 8 electron
How the shells fill with electrons
Element
Shell 1
Shell 2
Shell 3
Shell 4
Phosphorus 2 electron 8 electron
P
5 electron
0 electron
Sulphur
S
6 electron
0 electron
2 electron 8 electron
How the shells fill with electrons
Element
Shell 1
Chlorine
Cl
Argon
Ar
Shell 2
Shell 3
Shell 4
2 electron 8 electron
7 electron
0 electron
2 electron 8 electron
8 electron
0 electron
How the shells fill with electrons
Element
Shell 1
Potassium
Calcium
Ca
Shell 2
Shell 3
Shell 4
2 electron 8 electron
8 electron
1 electron
2 electron 8 electron
8 electron
2 electron
The First Twenty Elements
•
•
•
•
•
•
•
Hydrogen 1,0,0,0
Helium
2,0,0,0
Lithium
2,1,0,0
Beryllium 2,2,0,0
Boron
2,3,0,0
Carbon
2,4,0,0
Nitrogen 2,5,0,0
First 20 Elements continued
•
•
•
•
•
•
•
Oxygen
Fluorine
Neon
Sodium
Magnesium
Aluminium
Silicon
2,6,0,0
2,7,0,0
2,8,0,0
2,8,1,0
2,8,2,0
2,8,3,0
2,8,4,0
First 20 Elements continued
•
•
•
•
•
•
Phosphorus
Sulphur
Chlorine
Argon
Potassium
Calcium
2,8,5,0
2,8,6,0
2,8,7,0
2,8,8,0
2,8,8,1
2,8,8,2
The Alkali metals
• Lithium, Sodium and Potassium have one
electron in their outer shell and this is why
they are found in group one of the periodic
table.
The Nobel gases
• The Nobel gases have full outer shells and
they are found in group 0 of the periodic
table. Helium, Neon, Argon, Krypton,
Xenon and Radon.
The Halogens
• Fluorine, Chlorine, Bromine and Iodine are
the Halogens and they all have seven
electrons in their outer shell. This is why
they are found in group 7 of the periodic
table.
Displacement
• Fluorine can displace Chlorine, Bromine
and Iodine.
F
Cl
Br
I
Displacement
• Chlorine can displace Bromine and Iodine
but it cannot displace Fluorine
Cl
Br
I
F
Displacement
• Bromine can displace Iodine but it cannot
displace Fluorine or Chlorine
Br
I
F
Cl
Displacement
• Iodine cannot displace Iodine Fluorine,
Chlorine or Bromine
I
F
Cl
Br
Fluorine reacts with sodium
chloride. Which equation is
correctly shows this reaction?
•
•
•
F2 + 2Na  2NaF
F + Na  NaF
2F + 2Na  2NaF
Which will displace?
•
•
•
•
•
•
•
2NaF + Cl2  Yes or No
2NaBr + Cl2  Yes or No
2KI + I2  Yes or No
2LiCl + I2  Yes or No
2NaBr + I2  Yes or No
2NaBr + F2 Yes or No
Cl2 + 2NaBr  Yes or No
Four factors affecting
Reaction Rate
Catalysts
Concentration
Temperature
Surface Area
Catalyst
• A catalyst speeds up or slows down
a reaction but does not get used up
by the reaction.
Temperature
• If we increase the temperature of a
reaction by 100C the rate will
double this means the reaction will
be complete in half the time.
Concentration
• If we increase the concentration of
a reactant the number of particles
increase that in turn increases the
chance of a collision and initiates a
chemical reaction.
Surface area
• The larger the particle size the
smaller the relative area the slower
the reaction.
• The smaller the particle size the
greater the relative surface area and
the faster the reaction.
Group 1
• Lithium, sodium and potassium are all in
group 1.
• They all have one electron in the outer shell.
• They are all metals.
• They react with group 7 to form metal
halides.
Group 7
• Fluorine ,Chlorine, Bromine and Iodine.
• They all have 7 electrons in their outer
shell.
• They are all coloured.
• They form metal halides with group 1
metals.
Group 0
•
•
•
•
•
•
•
These are the noble gases.
They have complete electron shells.
The electron shells are full.
They are unreactive.
They are inert.
They do not react.
They include, Helium, Neon, Argon,
Krypton, Xenon and Radon
Halogens
Name
Colour
Fluorine Pale
Yellow
State
Gas
M.P.
-220
B.P.
-188
Chlorine Green
Gas
-101
-34
Bromine Brown
Liquid
-7
59
Iodine
Solid
114
184
Slate
grey
Reactions
•
•
•
•
•
•
Sodium and Chlorine react to form 
Sodium Chloride.
Iron and Chlorine react to form 
Iron Chloride.
2Na + Cl2  2NaCl.
Fe + Cl2  FeCl2.
Uses of the Halogens
• Fluorine is put into water supplies to kill
harmful bacteria and to help keep teeth
healthy.
• Chlorine is used in swimming pools to
bacteria in the water.
• Bromine is used in pesticides. Silver
bromide is used in photography.
• Iodine is an antiseptic on cuts and grazes.