In 1897 JJ Thomson “Plum Pudding” model for the atom.

small negative charges (“electrons”) arranged in a sphere of positive charge.

Rutherford “gold foil experiment”.

few positively charged particles were deflected backwards.

Bohr - Each shell represents an energy level. All electron in the same shell have fixed energy

-1 charge, 0.0005 mass

+1 charge, 1 mass

0 charge, 1 mass

Relative Atomic Mass – protons and neutrons

Atomic Number –protons (also number of electrons)

Neutrons = atomic mass – atomic numberAlways the

biggest number!

Isotopes – a form of an atom with the same atomic number (same number of protons) but a different number of neutrons so it has a different relative atomic mass.

Going down the periodic table the atoms are organised into groups.

Elements in the same group have the same number of electrons in

the outer shell.

They all have similar properties because they have the same

number of electrons in the outer shell.

Going across the periodic table the atoms are arranged into periods.

Elements in the same period have the same number of shells

In 1828, Dobereiner grouped the known elements into triads based on their chemical properties.

Middle element has the atomic mass which is the mean of the total atomic mass of the triad

Newlands every 8th element had similar properties so he organised them into groups of 7 called “octaves”.

His work was not accepted because:

1) Not all elements had similar properties.

2) mixed up metals / non metals

3) no space for undiscovered elements.

Mendeleev - elements in order of atomic mass.

groups according to similar properties.

left gaps - predicted properties of undiscovered elements.

Rules for drawing electron configuration

• Atomic number tells the number of electrons around the nucleus.

• Electrons always occupy shells (also known as energy levels)

• Lowest energy levels are always filled first.

• First shell – max 2 electrons

• Second shell onwards – max 8 electrons

• Ca – 2.8.8.2

Ionic Bonding• ions strongly attracted to each other. (+ to -)

• Group 1/2 are keen to lose electrons. • Groups 6/7 are keen to gain electrons• Metal – non metal

Na loses e- = positively charged.

Cl gains e- = negatively charged.

Ionic Compounds

• giant ionic lattices• ions strongly attracted to

each other / unable to move.

• high melting / boiling points

• don’t conduct electricity when solid

• When melted or dissolved - conduct electricity – ions free to move.

• Draw the ionic bonding for:– MgO– CaCl2

Covalent Bonding (strong)• non-metal atoms - share pairs

of electrons.• The forces between molecules,

are weak• very low melting / boiling

points.• don’t conduct electricity.

Methane (CH4)

Chlorine Gas (Cl2)

Water (H2O)Hydrogen Gas (H2)

Carbon Dioxide (CO2)

Group 1 – The Alkali Metals– Group 1 Metals - 1e-

in outer shell– go down group 1 -

metals more reactive.– outer electron further

away from nucleus so less energy is needed to remove it.

– all have low melting points, low density and are very soft.

• Reacting with water:– Move around the

surface, fizzing violently, produce hydrogen.

2Na + 2H2O 2NaOH + H2

Sodium + Water Sodium Hydroxide + Water

Alkali metals burn with characteristic colours:Lithium: RedSodium: YellowPotassium: Lilac

Group 7 – The Halogens• 7 e- in outer shell.• go down group 7 - less reactive• because there is less inclination to fill the outer shell

as its further from the nucleus.• Melting / boiling points increase.• At room temp:

– Cl2 is a poisonous green gas– Br2 is a poisonous orange liquid.– I2 is a grey solid

Halogens react with Alkali metals to form Metal Salts2Na + Cl2 2NaCl

Sodium + Chlorine Sodium Chloride

Displacement ReactionsA more reactive halogen can displace a less reactive halogen from its salt

chlorine + sodium bromide    →    sodium chloride + bromineCl2 + 2NaBr    →    2NaCl + Br2

Superconductors• At low temperatures• have little or no electrical

resistance.• benefits:

– Power transmission without loss

– Super-fast electronic circuits

– Powerful electromagnets– Superconducting

electromagnets used in hospital MRI scanners

Drawbacks:At the moment, superconductors have to be REALLY COLD. This is expensive

to achieve and takes a lot of energy.

Thermal Decomposition

• substance breaks down into two or more substances,when heated.

• Transition metal carbonates

• CuCO3 CuO + CO2• Test for carbon dioxide-

limewater-cloudy.CuSO4 + 2NaOH Cu(OH)2 + Na2SO4

Copper (II) Sulphate + Sodium Hydroxide Copper (II) Hydroxide + Sodium Sulphate

FeSO4 + 2NaOH Fe(OH)2 + Na2SO4Iron (II) Sulphate + Sodium Hydroxide Iron (II) Hydroxide + Sodium

Sulphate

Fe2(SO4)3 + 2NaOH 2Fe(OH)3 + 3Na2SO4Iron (III) Sulphate + Sodium Hydroxide Iron (III) Hydroxide + Sodium

Sulphate

Identifying transition metals• Add sodium hydroxide =

displacement reaction. • Na more reactive metal, displaces

transition metal • Transition metal hydroxide is

insoluble in water = precipitate.

Copper hydroxide: blue precipitateIron (II) Hydroxide: Grey/green precipitateIron (III) Hydroxide: Orange/Brown precipitate

WaterWater• reservoirs, lakes, rivers, bore holes, aquifers.• Pollutants get into water... Factory output, Leaks in pipes• Natural disasters• Bad sanitation• Waterborne disease• Lead pipes dissolving into the water• Pesticides• Nitrates from fertilisers

STEPS1. Sedimentation – particles drop to

the bottom2. Filtration – of particles using sand3. Chlorination – to kill microbes

PRECIPITATION reactions are used to test for the presence of IONS in water.

IONS to test for: Chemical usedSulphate SO4

2- ......... barium chloride – white precipitate

Barium chloride(aq) + sodium sulfate(aq)→sodium chloride(aq) + barium sulfate(s)

BaCl2(aq) + Na2SO4(aq) → 2NaCl(aq) + BaSO4(s)

Chloride Cl- WhiteBromide Br- ……… silver nitrate CreamIodide I- Pale Yellow

Silver nitrate(aq)+sodium bromide(aq)→sodium nitrate(aq)+silver bromide(s)

AgNO3(aq) + NaCl(aq) → NaNO3(aq) + AgCl(s) Write BALANCED symbol equations for these :

1. Silver nitrate + Sodium chloride2. Silver nitrate + Sodium bromide3. Silver nitrate + Sodium iodide

MOLESMOLES

• The mass of one mole is its molar mass (RFM in grams)

For example ... Hydrogen's RFM is 1 ... Its molar mass is 1g

• RFM is relative to 1/12 carbon

Mass (g)

Molar mass

Amount of moles

Volume (dm3)Concent

ration

Amount of moles

In 1 mole there are 6.02x10^23 particlesAvagadro’s number = 6.02x10^23

1. How many moles are there in 66g Carbon Dioxide?

2. What mass of carbon is there in 4 moles of carbon

dioxide?

Converting concentration from mol/dm3 to g/dm3 You have a solution of sulphuric

acid of 0.04mol/dm3. What is the concentration in g?STEP 1: Work out RFMH2SO4 = 98STEP 2: Convert the conc in moles to conc in grams. So in 1dm3Mass = moles x RFM0.04 x 98 = 3.92 g

• Calculate the mass of aluminium oxide when 135g of aluminium is burned in air.

• Step 1: Write the balanced equation for the reaction

• (4Al + 3O2 2Al203)

• Step 2: Calculate the moles for the part you have the information for.

(moles of aluminium = 135/ 27 = 5)

• Step 3: Look at the ratio to give you the moles for the part that you want.

(4 moles of Al react to form 2 molesAl2O3 so 5 moles would give 2.5 moles of aluminium oxide)

• Step 4: Use the equation mass = moles x Mr

(mass of aluminium oxide = 2.5 x 102 =255g)

• empirical formula shows you the simplest ratio of atoms in a compound (C2H6 would become CH3.).

• To calculate this, all you need is the experimental masses and the relative atomic mass (Ar), which is found on the periodic table.

• Example: Find the empirical formula of iron oxide when 44.8g of iron reacts with 19.2g of oxygen

• There are 5 steps:

• 1) List the elements -• 2) Write down the experimental masses -• 3) Divide each experimental mass by the Ar of each -• 4) Divide by smallest

• What is the empirical formula of • a) C7H14?

• b) C6H12O6?

• c) Al2O6?

• Find the empirical formula when:

• a) 2.4g of carbon react with 0.8g of hydrogen

• b) 21.9g of magnesium react with 29.3g of sulfur and 58.3g of oxygen

Titrations• Titrations are used to find out

exactly how much acid is needed to neutralise an alkali or vice versa.

• It can then be used to calculate unknown concentrations.

• Method:– Fill a conical flask with 25cm3

alkali of unknown concentration– Add 2-3 drops indicator– Fill a burette with acid– Using the burette add the acid a

bit at a time (say 5cm3)– When indicator changes colour

you have reached the end point. You now have a rough estimate of how much (to the nearest 5cm)

– Now repeat adding a smaller amount of acid each time.

– To increase the accuracy you need to get several consistent readings!

Titrations use single indicators so it makes it easy to see the

end point of the titration.

E.G phenolphthalein

Universal indicator is made from a mixture of different indicators so each colour indicates a range

of pH values.

• Concentration = moles x volume

• You start off with 25cm3 of sodium hydroxide that has a concentration of 0.100 moles per dm3. It takes 49cm3 of hydrochloric acid to neutralise the sodium hydroxide. What is the concentration of the hydrochloric acid used?

• Step 1: Work out how many moles of the “known” substance you have.• Number of moles = conc x volume

= 0.1 x (25/1000) = 0.0025 moles of sodium hydroxide

• Step 2: Write the balanced symbol equation for the reaction. Work out how many moles of the “unknown” stuff you had.

• NaOH + HCl NaCl + H2O• For every mole of NaOH, you need one mole of HCl• So you must need 0.0025 moles of HCl

• Step 3: Work out the concentration of the “unknown” stuff!• Concentration = no of moles / volume

= 0.0025 / (49/100) = 0.0510 mol/dm3

When you do a titration there is a gradual change in pH. At the end point there is a sudden change in pH.

The rate of a reaction can be measured by the amount of gas

produced.

Gas Syringe

Upturned measuring cylinder/burette

Mass Loss

Method Pros Cons

Gas Syringe

Can be used to collect pretty much any gas.Accurate volumes – to the nearest cm3

If the reaction is too vigorous it can blow the plunger out of the syringe.

Upturned measuring

cylinder

Cannot collect gases such as Hydrogen chloride or ammonia as these dissolve in water.

Accurate volumes – to the nearest cm3

Mass Loss Gas is released straight into the room so not suitable for reactions that produce poisonous gases.

Greater accuracy.

Time

Am

ount

of P

rodu

ct

Interpreting Rates of Reaction

Steeper gradient – faster rate of reaction

End of Reaction

More reactant

Equilibrium• Haber Process • N2 + 3H2 2NH3

• equilibrium – rate of the forward reaction is equal to the rate of the backward reaction

• closed system

Reaching an Equilibrium – the Haber Process

1)As nitrogen and hydrogen react together their concentrations fall. The initial rate of reaction

will begin to slow down.2) As more and more of the product ammonia is made, its

concentration rises and it begins to turn back into nitrogen and

hydrogen.3) As more is made, the rate of the reverse reaction speeds up. 4) After a while the forward reaction will be going at the same rate as the backward

reaction.

EquilibriumEquilibrium

• The position of the equilibrium can be in the middle, to the left or to the right.

• This tells us about the amounts of the products and reactants.• If the equilibrium is in the middle then there are the same

amounts of reactants as products.• If the equilibrium is to the right then there is more product and

not so much reactant.• If the equilibrium is to the left then there is more reactant and

not so much product.

C5

Reactant

ProductReactant

Product

Changing Equilibrium• Three factors affect the position of the equilibrium:

TemperatureFor all reversible reactions, one direction is an exothermic

reaction and the reverse direction is endothermic.• decrease temperature - rate of endothermic reaction

decreases•equilibrium will shift towards the exothermic reaction so

that more heat is produced.Pressure (only for gases)

increase pressure-equilibrium tries to reduce itequilibrium moves in the direction where there are fewer moles of gas

ConcentrationIncrease concentration-equilibrium tries to reduce this (so more product is made) = shifts to reduce this so more turns back into the reactants.

The contact processThe contact process1.)Burn sulphur in air to make

sulphur dioxide S + 02 SO22.)React sulphur dioxide with

more oxygen in air to create sulphur trioxide

2SO2 +02 2SO33. React SO3 with water to

makes sulphuric acidSO3 + H2O H2SO4

• 450 oC -compromise, forward reaction is exothermic so high temps reduce yield and shift equilibrium to left. But, at high temps rate of reaction is quicker so chemical is produced faster

• Atmospheric pressure-compromise, 3 gas molecules on the left and 2 on the right so high pressure increases yield by forcing equilibrium to the right. However, equilibrium already lies to right so the cost of thicker walls etc. to withstand higher pressure is not economical

• vanadium pentoxide (V2O5)does not affect the position of the equilibrium but makes the reaction go faster

Strong and Weak Acids• Strong Acids ionise completely in water. This means that

the compound dissociates (e.g HCl H+ + Cl-). There is a higher concentration of H+ ions ready to react.

• Weak Acids only partially ionise in water. It is a reversible reaction which sets up an equilibrium mixture.

• (e.g CH3COOH H+ + CH3OO-)• Only a few H+ ions are released at once so the

equilibrium is off to the left.• Once these H+ ions have been used up a few more are

released.• Strong acids are better electrical conductors because

they have a higher concentration of hydrogen ions to carry the charge.

Redox Reactions• Oxidation is Loss,

• Reduction is Gain• OIL RIG• Oxidising Agent – accepts

e-• Reducing Agent – donates

e-

Preventing Rusting1) Making alloys e.g steel

2) Painting and oiling/greasing

3) Galvanising – coating with a tin plate

4) Sacrificial Protection – place a more reactive metal with the iron. The water and oxygen will react with this instead.Iron + Water + Oxygen Hydrated iron(III)oxide

• Electrolysis of aqueous sulfuric acid.

• Ions: H+, OH-, SO42-

• Hydrogen ions accept electrons from the cathode to make hydrogen gas.

• At the anode, hydroxide ions lose electrons to make oxygen gas

• Products: Cathode: Hydrogen 2H+ +2e- H2Anode: Oxygen 4OH- -4e- O2 + H20

• Electrolysis of copper sulfate using carbon electrodes.

• Ions: Cu2+, H+, OH-, SO42-• Copper ions accept

electrons from the cathode to make copper.

• At the anode, hydroxide ions lose electrons to make oxygen gas

• Products: • Cathode: Copper Cu2+ +2e- CuAnode: Oxygen 4OH- -4e- O2 + H20

which anion/cation is easier to discharge?The ion discharged first is the one which is lower in the reactivity series.

What’s the link between current and charge when talking about electrolysis?• The amount of product is proportional to time and

current• Q = It• t Time (seconds)• I Current (amps)• Q Charge (coulomb)• Example question:

– A current of 0.1A for 2 hours increased the mass of an anode by 0.24g. How much charge was transferred?

http://www.youtube.com/watch?v=6UwSazq8GTU

Pollution•Contain poisonous catalyst•Burn fossil fuels to produce hydrogen and oxygen

Making EthanolFermentation•Renewable – raw material from plant material•Yeast is used to ferment glucose solution•glucose→Ethanol+Carbon Dioxide•C6H12O6 → 2C2H5OH + 2CO2•(enzyme inactive) 25 - 50 degrees (denatured)•Absence of air from fermentation prevents the formation of ethanoic acid by oxidation of the ethanol.•slow•Ethanol purified by distillation, lots of energy, expensive

Hydration•Ethene Ethanol

•Ethene passed over heated phosphoric acid catalyst with steam.•Ethene + water → Ethanol•C2H4 + H2O → C2H5OH

•non-renewable as the ethene will be made by cracking components of crude oil. •quicker

Depletion of Ozone• In stratosphere• Ozone filters out and stops harmful ultraviolet light from reaching the surface of the earth• CFCs were used as refrigerants and in aerosols because they have a low boiling point, are

insoluble in water and are very unreactive.• Use of CFCs in the UK is now banned to stop any more damage to the ozone layer.• Instead hydrocarbons (alkanes) or hydrofluorocarbons (HFCs) are now used as safer

alternatives to CFCs.• The depletion of ozone in the atmosphere allows increased levels of harmful ultraviolet light to

reach the earth and this can cause……– An increased risk of sunburn– Increased ageing of the skin– Skin cancers– Increased risk of cataracts

Free Radicals• CFC molecule is hit by UV light a chlorine atom is produced. A chlorine atom is called a free

radical.– The chlorine free radical reacts with an ozone molecule to form a chlorine oxide molecule and an

oxygen molecule

• Cl + O3 → ClO + O2 – The chlorine oxide molecule then reacts with an oxygen atom to produce a chlorine free radical and an

oxygen molecule

• ClO + O → Cl + O2 – The chlorine free radical is regenerated by this chain reaction and can go on to destroy many more

ozone molecules in a a chain reaction. Therefore a few chlorine atoms can destroy large amounts of ozone.

Water Hardness– Hard = does not lather with soap– Soft = lathers well with soap

• Calcium and magnesium ions form dissolved salts which cause hardness in water

• There are two types of hardness in water– Permanent = caused by dissolved calcium sulphate. Cannot be

removed by boiling– Temporary Calcium carbonate + water + carbon dioxide calcium hydrogencarbonateCan be removed by boilingDecomposition of Ca(HCO3)2

Ca(HCO3)2 CaCO3 + H2O + CO2 (insoluble limescale)Removes temp. and permanent1. Ion Exchange resin –- sodium ions come off the resin and go into the

water, while calcium ions come out of the water and stick to the resin 2. Washing Soda – Na2CO3

Ca2+(aq) + CO3

2–(aq)→ CaCO3(s) Insoluble Limescale

(solids) Fats and Oils (liquids)Oils and fats are ESTERS that can be obtained from animals or vegetables.

– Saturated = carbon-carbon single bonds– Unsaturated = at least one carbon-carbon double bond

Test for Unsaturated fats• Shake with bromine water : Orange to colourless Natural Fats and Oils• Animal oils/fats often saturated - Vegetable oils/fats often unsaturated• More unsaturated = reduce build up of cholesterol.Mixing Fats and Oils• Oil and water are immiscible - do not mix.• vegetable oil added to water + shaken well = emulsion.• An emulsion is one liquid finely dispersed in another • The shaking breaks up the oil into small droplets that disperse (spread out) in the

water.– Milk is an oil-in-water emulsion that is mostly water with tiny droplets of oil

dispersed in it.– Butter is a water-in-oil emulsion that is mostly oil with droplets of water dispersed

in it.Saponification - vegetable oil + hot sodium hydroxide glycerol + soap• hydrolysis - breaking up ester groups in the oil molecule using an alkali• Margarine : vegetable oil + hydrogen : nickel catalyst solid saturated fat

Detergents• hydrophilic head forms strong intermolecular forces with water molecules• hydrophobic tail forms strong intermolecular forces with fat and oil molecules

Dry cleaning • A greasy stain may be removed using dry cleaning solvent.• There are weak intermolecular forces between the grease molecules, and

there are weak intermolecular forces between the solvent molecules.• The solvent molecules can also form intermolecular forces with the grease

molecules. This lets the solvent molecules surround the grease molecules.