1 of 7

Structure of the atom:

Models of the atom:

C1 - Atomic Structure

Discovered electrons

Discovered nucleus

Discovered energy levels

Subatomic particle	Relative charge	Relative mass	Location
Proton	+	1	Nucleus
Neutron	nil	1	Nucleus
Electron	-	Almost 0	Orbiting the nucleus

Key definitions:

Separating mixtures:

Molecule:	2 or more atoms bonded together	Compound:	Substance made from 2 or more types of atom bonded together
Element:	Substance made of 1 type of atom	Isotopes:	2 atoms with the same number of protons and different numbers of neutrons
Solution:	A mixture of a liquid (solvent) and a soluble solid (solute)	Mixture:	2 or more substances in the same place but not bonded together

	Filtration	Separates an insoluble solid from a liquid
	Crystallisation	Separating the solute (dissolved solid) from a solution
	Distillation	Separates the solvent (liquid) from a solution
	Fractional distillation	Separates miscible liquids because they have different boiling points.
	Chromatography	Separates soluble substances using a solvent

�+

→

2 of 7

C2 - Periodic Table

Dalton

- List of elements

Newlands

- Law of octaves

Arranged by mass

Mendeleev

Left gaps

Swapped elements (Te - I)

Arranged by properties

Moseley

- Discovered protons

Arranged by atomic number

Groups - Same electrons in outer shell (have similar chemical properties)l

Periods - Same number of shells

Group 1 - Alkali metals

Alkali metals have characteristic properties because of the single electron in their outer shell.

- Alkali metal + water → alkali metal hydroxide + hydrogen

- Alkali metal + chlorine → Alkali metal chloride

- Alkali metal + oxygen → Alkali metal oxide�

More reactive down group

Because:

More electron shells

Outer shell electron easier to remove

Group 7 - Halogens

Less reactive down group

Because:

More electron shells

Harder to gain electron

Group 0- Noble gases

Unreactive

Full outer shell

Sodium iodide + chlorine → Sodium chloride + Iodine

Displacement

More reactive halogen displaces less reactive

Development of the Periodic table

Arrangement of the Periodic table

Ordered by atomic number

The majority of the element are metals

Metals react to form positive ions.
Non-metals react to form negative ions.

Transition Metals’

Good conductors of electricity, hard and strong, high density, high melting points

Many transition elements have ions with different charges, form coloured compounds and are useful as catalysts.

3 of 7

Covalent Bonding - Between non metals

Pairs of electrons shared

No ions are formed

C3 Structure & Bonding

Simple covalent structures

Strong covalent bonds

Weak intermolecular forces

(attraction between the individual molecules)

Low melting and boiling points

Does not conduct electricity

===

Giant covalent structures

Contain many atoms joined by strong covalent bonds.

Examples :

Graphite - each carbon is covalently bonded to 3

other carbon atoms.

Delocalised electrons free to carry charge

Layers can slide over each other

Diamond - Each carbon atom is covalently bonded to 4

other carbon atoms

Does not conduct electricity

Very hard

High melting and boiling points

⇆

Metallic bonding

Positive metal atoms

Sea of delocalised electrons

Strong electrostatic force of

attraction between + nuclei and

delocalised electrons

High boiling and melting points

Delocalised electrons free to carry charge throughout the structure

Ionic bonding - Between metals and non metals

Ion - charged particle formed when an atom gains or loses electrons.

Metal atoms transfer electrons to non metal atoms to complete outer shells

Strong electrostatic force of attraction between positively (metal) and negatively charged (non metal) ions.

Ions form giant lattices

High melting and boiling points

Liquid / molten: charged ions can move and carry current

Solids: ions cannot move so cannot carry current

Chemistry paper 1

4 of 7

C4 Chemical calculations

Keywords
Relative atomic mass	Number of neutrons and protons in an atom - A_r
Relative formula mass	Total mass of the atoms in a molecule - M_r
Mole	M_ror A_r in grams Mass of 6.02x10²³ atoms of a substance
Limiting reactant	The reactant that will be used up first.

Reacting masses
Sometimes we need to work out the mass of a product we are going to male from a set amount of reactants or work out the amount of reactants we need to make a desired amount if a product
Step 1: Write and balance the chemical equation Step 2: Work out the number of moles of the molecule you know the mass of. Step 3: Multiply by the number of molecules of the known substance Step 4: Divide by the number of molecules of the molecule you are working out the mass of. Step 6: Multiply by the M_r of the molecule you are trying to find the mass of
Equation: Unknown mass = M_r unknown x molecules known x mass known M_r known molecules unknown

% Yield
The % yield tells us how effective the process we are using is
Formula:	% Yield = Actual mass produced x 100% Max theoretical mass
The yield is never 100% because: The reaction may be reversible. There may be alternative reactions occurring. Some of the product may be left in the apparatus. The reactants may not be pure. Some might be lost as the product is separated from reactants/other products

Titration
Used to work out the concentration of an acid or alkali
	Step 1: Use a volumetric pipette to get a known volume of the test solution
	Step 2: Put into a conical flask and add an indicator
	Step 3: Add a known volume of a known concentration of acid or alkali (opposite to what you started with) to a burette
	Step 4: Add drops of solution from the burette, swirling between drops until the indicator shows a permanent colour change.
Step 5: Concentration_A = concentration_Bx volume_Bx molecules_B volume_A x molecules_A

Atom economy
Atom economy important in industrial reactions as reactions with high atom economy create less waste.
Formula	% Atom economy = M_rof desired product x 100 Sum of M_r of all reactants

Masses to equations
If we know the masses of reactants and products we can work out the balanced formula
Step 1: Work out how many moles of the reactants you had Step 2: Work out how many moles of the products you have Step 3: Set up as a ratio Step 4: Create the smallest whole number ratio

5 of 7

C5 - Chemical change

Keywords

Ion

When an atoms gains or loses electrons

Oxidation

The gaining of oxygen OR the loss of electrons (OIL)

Reduction

The loss of oxygen OR the gain of electrons (RIG)

Displacement Reaction When a more reactive substance takes the place of a less reactive substance

General word equations

Metal + oxygen → Metal oxide

Metal + water → Metal hydroxide + hydrogen

Metal + acid → Metal salt + hydrogen

Acid + base → Salt + water

Acid + alkali → Salt + water

Acid + carbonate → Salt + water + carbon dioxide

Base

Ionic compounds that can neutralise acids

Alkali

Soluble bases

potassium

sodium

calcium

magnesium

aluminium

carbon

zinc

iron

tin

lead

hydrogen

copper

silver

gold

platinum

The Reactivity Series - metals in order of reactivity

Most reactive’

least reactive

Least reactive metals occur native (not bonded to other elements).

More reactive elements are found in ores

For metals less reactive than carbon, carbon can be used to reduce the metal in a displacement reaction.

Some less reactive metals can be reduced using hydrogen

Common salts

Hydrochloric acid (HCl) → chlorides (Cl^-)

Sulphuric acid (H₂SO₄) → sulphates (SO₄^2-)Nitric acid (HNO₃) → nitrates (NO₃^-)

Charges on positive ions

Group 1 metals = +1

Ammonium (NH₄⁺) = +1

Group 2 metals = +2

Aluminium = +3

Charges on negative ions

Group 7 = -1

Nitrate (NO₃^-) = -1

Hydroxide (OH^-) = -1

Sulphate (SO₄^2-) = -2 Carbonate(CO₃^2-) = -2

Oxidation

Loss (of electrons)

Reduction

Gain (of electrons)

6 of 7

Electrolyte

An liquid containing free moving ions that can be broken down by electrolysis.

Cathode (negative electrode)

Anode (positive electrode)

Power supply

Electrolysis

The breakdown of a substance containing ions using electricity

Ion

The charged particle formed when an atom gains or loses electrons.

Ions are attracted to the electrode of the opposite charge

C6 Electrolysis

Most reactive’

Anode = negative ions (anion) are attracted which will be a non- metal. The will lose electrons (oxidised)

What is given off/collected?

A group 7 ion (halogen) is present (Cl^-,Br^-,F^-)
Otherwise OH^- ions form oxygen molecules.

2Cl^-_(aq) → Cl_2(g₎+ 2e^-

4OH^-_(aq)→ 2H₂O_(l)+ O₂_(g)+ 4e^-

Cathode = positive ions (cation) are attracted which will be a metal or hydrogen

What is given off/collected?

If a molten solution the metal (positive) ion is collected
If it is an aqueous solution,, you have hydrogen and metal ions. The least reactive is given off

2H⁺_(aq) + 2e^- → H_2(g)

Cu²⁺_(aq) + 2e^- → Cu_(s)

Extraction of Aluminium

Aluminium is malleable, strong and light. It is used for cans, aeroplanes and overhead power cables

Purify bauxite to get alumina (Al₂O₃)

Electrolysis of (Al₂O₃)

Cryolite is used to reduce the temperature required to melt the Al₂O₃

Carbon electrodes react with oxygen produced to form CO₂ so they need to be replaced regularly.

cathode

anodes

7 of 7

C7 - Energy Changes

Exothermic reactions

Transfers chemical energy to the surroundings - usually as heat.

The temperature will increase.

energy

Course of reaction

reactants

products

Activation energy, E_a

The energy needed to start a reaction.

E_a

Enthalpy change (overall energy change)

Endothermic reactions

A reaction that takes in energy from the surroundings and transfers it to a chemical store. The temperature will decrease.

energy

Course of reaction

reactants

products

E_a

Enthalpy change

Bond breaking takes in energy - endothermic

Bond making releases energy - exothermic

Bond Energy

Add up the amount of energy required to break all of the bonds in the reactants.

Add up the energy released when the products are formed.

Total energy required - total energy released

-ve = exothermic reaction

+ve = endothermic reaction

Combustion

Respiration

Uses for exothermic reactions

Self heating cans

Handwarmer

Thermal decomposition

Photosynthesis

Uses for endothermic reactions

Cool packs, for sports injury

Chemical cells and batteries

Electrodes made of metals of different reactivities

The most reactive metal donates electrons to the less reactive metal via the external circuit.

Cathode - made of the most reactive metal

Anode

Electrolyte

Fuel cells

Combines hydrogen and oxygen to form water. The energy released is transferred via an external circuit by electrical working.