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JM

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An atoms nucleus contains protons and neutrons
...

Isotopes are atoms with the same number of electrons but a different number of
neutrons
...

Electron arrangement in carbon:
Electron configuration = [2, 4]
Group 8 elements (noble gases) with a
full outer shell are unreactive
Horizontal rows are called Periods – tells you the number
of electron shells
...
Elements in the same group
have similar reactivities
...
g
...
Sodium 2,8,1 loses one electron (easier to lose
one electron than to gain seven), chlorine gains one electron to get a
full outer shell
...

• When an atom loses an electron they are left a positive charge
(Na+)
...

• During chemical bonding ions are formed
...

There is a quick way to work out what the charge on an ion should be:
• the number of charges on an ion formed by a metal is equal to the
group number of the metal
• the number of charges on an ion formed by a non-metal is equal to
the group number minus eight
• E
...
Magnesium forms Mg2+ ions, Oxygen forms O2- ions
• Ionic bonding can be represented by dot and cross diagrams
•
•

Covalent
•
•
•

Bonding between non-metals and non-metals
The atoms share electrons in order to get full outer shells
...


Methane

1) Simple Molecular Structures
Small molecules containing few atoms (e
...
H2O, CO2)
Strong covalent bonds between atoms
Forces between molecules are fairly weak (weak intermolecular
forces)

Typical Properties:
• Low melting point and boiling point because forces between
molecules are weak
•

Do not conduct electricity

2) Giant Ionic Structures
• Ions held together by strong ionic bonds so have high
melting points
• Ions are not free to move in solid so do not conduct
electricity
• Ionic compounds conduct electricity
when heated to become molten
or dissolved in water because ions
are free to move

3) Giant Covalent Structures
•
•
•
•
•
•
•

Large network of bonds – giant covalent
Substances such as: diamond, graphite and silicon dioxide
Held together by very strong covalent bonds
High melting and boiling points because they have strong covalent
bonds
...

Fullerenes: carbon’s ability to make large cage like structures
...

The atoms in metals share their outer electrons with all
the other metal atoms, so that a metal consists of positive
ions surrounded by a sea of delocalised electrons
...

The forces of attraction between the positive ions and outer
shell electrons(called metallic bonds)are very strong
...


Alloys
Pure metals have atoms arranged in a regular
pattern and the layers of atoms can easily slide
over one another when a force is applied making
them too soft for use in construction
...
They are stronger than pure
metals
...
If
we bend them into a
different shape or
heat them, they
return to their
original shape by
themselves – these
are called smart or
shape memory alloys
...
g
...
devices that cause movement
when the temperature changes

e
...
Thermostat
in kettles: (when
it starts to boil
steam makes the
alloy change
shape and switch
off the current)

2
...
g
...
shape change is restricted,
creating stress
e
...
braces
made from
smart alloy –
when the alloy
warms up in
the mouth it
goes back to
its original
shape, pushing
teeth into the
right position

4
...
Superelastic alloys have a
memory and when bent or
stretched will return to their
original shape

Superelastic alloys are
used in spectacle
frames

The properties of polymers depend on what they are made of
and by which method they are made
...


Low Density

High Density

There are two types of plastic:
Thermosoftening
These plastics are flexible and
melt when heated because there
are weak intermolecular forces
between the polymer chains so
they can slide over each other
easily
...

Nanoparticles range in size from about
100nm down to about 1nm
...

They can, for example, be used in self-cleaning ovens and
windows
...
For example, titanium
dioxide is a white solid used in house paint and certain sweetcoated chocolates
...
They are used in sun screens
to block harmful ultraviolet light without appearing white on
the skin
...
The Ar
values of the atoms in a formula are added to get the relative
formula mass or Mr
H2SO4 = 1x2 + 32 + 16x4 = 98
Mg(NO3)2 = 24 + (14 + 3x16)x2 = 148
Percentage Calculations
If you need to find the percentage of an element in a compound,
you use the formula:
Percentage =

Ar x No of atoms x 100
Mr of compound

e
...

Find the percentage of nitrogen in ammonium nitrate (NH4NO3)
Mr of N = 15
No of N atoms = 2
Mr of ammonium nitrate = 14 + 4 x 1+ 14 + 3 x 16 = 80
Percentage of nitrogen = 2x14x 100 = 35%
80

Empirical Formulae (Higher Tier Only)

•This is the formula which shows the lowest whole number ratio of the
atoms
• e
...
Molecular formula = C2H4, Empirical Formula = CH2
• To calculate an empirical formula
• Find the mass (or %) of each element present
• Divide each of these masses by the relative mass of that element
• Divide each number obtained in stage 2 by the smallest of those
numbers
...


20g of a compound of Silicon with hydrogen contains
17
...
Find the empirical formula
...
5

20-17
...
5

Relative Mass (Ar)
Mass ÷ Ar

28
17
...
625

1
2
...
5

Divide through by
smallest
...
625 ÷ 0,625 = 1

2
...
625 = 4

1

4

Whole Number Ratio
Empirical Formula

SiH4

Equation Calculations
In these, you will always be given the mass of one substance and
be asked to find the mass of another substance
MOLES; MOLES; MASS !!

Moles of the one you know
Moles of the one you don’t
Now work out the unknown mass

Mass
Mr

Moles

What mass of carbon dioxide is obtained by burning 3g of C2H6?
2C2H6 + 7O2 = 4CO2 + 6H2O
Mr: C2H6 = 30, CO2 = 44
Moles of C2H6 = Mass = 3 = 0
...
2
Mass of CO2 = Mr x Moles = 44 x 0
...
8g

Atom Economy
This is given as

Formula Mass of all molecules of Useful Product x 100
Formula Mass of all molecules of Reactants

Eg
...
9%
244

Paper chromatography is a form of
separation that allows analysis of food
additives or dyes in pens
...


The rate of reaction is how fast a reaction happens
• We can measure this by: the mass of a mixture, the
volume of gas given off, measure the light transmitted
...

Rate of reaction = amount of a reactant used or amount of product formed
Time

Collision Theory

• Affected by the temperature, concentration, surface area,
pressure and whether there is a catalyst
...
They
must collide with enough energy otherwise they will not react
...


Concentration
Higher concentration means more particles in the same
volume so the reaction is faster because there are more
collisions per second
Remember: increasing concentration or pressure does not
increase the energy with which the particles collide
...


Surface Area
Smaller pieces of materials have an increased surface area for
a reaction to take place so more collisions per second
...
The collisions are more energetic
...

A catalyst is something which increases the rate of a reaction but
it is not affected chemically itself at the end of a reaction
...

Catalysts are often very expensive as they are made of precious
metals
...

Some catalysts work by providing a surface for the reacting
particles to come together
...

Catalysts often come in the form of powders, pellets or fine
gauzes, this provides the largest possible surface area for them to
work
...

Transferring energy from the reacting chemicals to the
surroundings is called exothermic reactions
...

Transferring energy from the surroundings to the reacting
chemicals is called endothermic reactions
...

Neutralisation between acids and alkalis is exothermic
...


Pure water is neutral on the pH scale
When we dissolve a substance we make an aqueous substance
The (aq) symbol shows that the ions are in an aqueous
solution
...

Bases can neutralise acids
...
(i
...
they are soluble
bases)
All acids form H+ ions when we add them to water – it is the
hydrogen which makes solutions acidic
...

All bases form hydroxide ions (OH-) when we add them to
water
...


Some examples of acids, alkalis and neutral substances
Acid

Neutral

Alkali

Sulphuric Acid

Water

Sodium Hydroxide

Citric Acid

Alcohol

Potassium Hydroxide

Hydrochloric Acid
Nitric Acid
Carbonic Acid

Ammonia

From metal and acid
We can make salts by reacting acids
with metals
•This only works if the metal is above
hydrogen in the reactivity series
•When the acid reacts with a more
reactive metal, hydrogen gas is
produced along with a salt
...
This type of salt is soluble
...

This makes an insoluble salt, which is called a precipitation
reaction because the insoluble solid is called a precipitate
...
When you
mix their solutions together, you make soluble sodium nitrate
and insoluble silver chloride:
silver nitrate + sodium chloride → sodium nitrate + silver chloride
AgNO3(aq) +
NaCl(aq)
→ NaNO3(aq) +
AgCl(s)

The silver chloride appears as tiny particles suspended in the
reaction mixture - it forms a precipitate
...


Method for acid + insoluble base
1
...

2
...

3
...
g
...


Conductors
Metals and graphite are the only solids which conduct electricity,
but no chemical change is involved
...

Electrolytes
These are liquids which conduct electricity, and are decomposed by
it
...
This includes all acids and metal compounds
...


Non-electrolytes are covalent substances, e
...
pure water, sugar
solution, alcohol, petrol
...

Electrons enter the solution through the negative electrode
(cathode), cause a chemical change and leave by the positive
electrode (anode)
...

The metal is produced at the cathode (-), while the non-metal is
produced at the anode (+)
e
...
Lead Bromide (molten) = Lead (at the cathode) + Bromine (at the anode)

PbBr2

→

PB (I) + BR2 (g)

With aqueous electrolytes, the electrolyte is also split up, but if the
metal is reactive, then hydrogen from the water is produced at the
cathode in place of the metal
...
g
...
g
...

When an ion reaches the electrode they either lose or gain an electron
depending on their charge
...

Gaining electrons is called reduction
...


O xidation
Is
L oss
R eduction
Is
G ain

Electrolysis of Sodium Chloride Solution
The main ions present in sodium chloride solution are Na+ and Cl-,
but there are also a few H+ and OH- ion present because water is very
slightly ionised
...
Here
the H+ ions pick up electrons, since hydrogen is less reactive than
sodium
...


2H+ + 2e- = H2
The Cl- ions are attracted to the positive anode
...
These atoms pair up
to form chlorine molecules
...


2Cl- = Cl2 + 2eThe products are hydrogen and chlorine, but Na+ and OH- ions are
left in solution to make sodium hydroxide (NaOH)
Uses of products:
Chlorine: Purifying water, making PVC plastic
...

Sodium Hydroxide: Making soap
...

The H+ ions and Cu2+ are attracted to the cathode but Cu gains
electrons (reduction) more easily so that copper is deposited
Cu2+ + 2e- → Cu
At the anode, rather than the sulphate or hydroxide ions releasing
their electrons, the atoms in the copper anode release their electrons
(oxidisation) and form ions that then enter solution
Cu → Cu2+ + 2eTherefore, at the cathode, copper ions from solution are being
deposited, and the cathode increases in mass
...
The
concentration of copper ions in solution remains unchanged
...
g
...

Electroplating
Electroplating allows a thin layer of one metal to be deposited on
another
...
g
...

The object to be plated is placed as the cathode, while the metal to coat
it is placed as the anode
...

e
...
to nickel plate a piece of iron, the iron would be the cathode, the
nickel would be the anode and the solution would be nickel sulphate
...

Ni2+ + 2e- → Ni
These ions would then be replaced by Nickel metal slowly dissolving
from the anode
...

Cryolite is used to lower the melting point of aluminium
oxide
Graphite electrodes are used
Aluminium forms at the negative electrode and oxygen at
the positive electrode
...

CO2



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