C4 - Information

C4a - Atomic structure

• Electron charge -1 mass 1/2000
• proton charge 1 mass 1
• Neutron charge 0 mass 1
• An atom is neutral because it contains an equal number of protons and electrons
• Atoms radius is 10"-10 mass is 10"-23
• Isotopes are a variety of an element that have the same number of protons and electrons but a different number of nutrons
• Electron structure of calium 2.8.8.2
• Isotopes are named after their mass number e.ge carbon - 12
• 1803 - Daltons model of an atom
• 1897, JJ Thomson discovered the electron
• 1911, Ernest Rutherford said the atom had a nucleus surrounded by a ring of electron. He broved Niels Bohrs plum pudding model wrong
• Unexpected results(e.ge geiger and Marsden's experiment) led to the Rutherford's theory of a nuclear atom
• Their exaplainations were provisional . When more evidence was available their theory or model could be developed further
• Theory changed as new evidence was found

C4b - Ionic bondin

• An Ion is a charged atom(loses or gains electrons)
• If an atom loses one or more electrons, it becomes a positively charged ion
• If an atom gains one or more electron, it becomes a negatively charged atom
• Metal atoms(usually form positively charged atoms)
• Non metals (usually form negatively charged atoms)
• Ionic bonding:
• When a metal reacts with a nonmetal, electrons are transferred from the metal atoms to the nonmetal atoms.
• The positive metal ions and the negative nonmetal ions attract one another forming ionic bond
• ""Dot and cross diagrams show ionic bonding""
• Ionic compounds:
• sodium chloride and magnesium oxide do not conduct electricity when they're solid.
• electric current cannot pass through because ions aren't able to move.
• Sodium chloride and magnesium oxide conduct electricity when moltern because ions can move.
• The structure of sodium chloride and magnesium oxide is a Giant ionic lattice - which posotive ions have strong electrostatic attractions to negative ions.
• The giant ionic lattice makes their melting point high so a lot of energy is needed to break it apart.
• Why magnesium oxide has a higher melting point than sodium chloride:
• Magnmesium atoms donates two electrons to each oxygen atom making a stronger ionic bond. Sodium chloride only donates one electron.
• Magnesium ions are very small in radius, so can get closer to oxygen, makes ionic bond strength higher. More energy is needed to seperate these ions than is needed to separate sodium an chloride ions.

C4c - The periodic table and covalent bonding

• Non - metals combine together by sharing electrons - covalent bonding
• ""Dot and cross diagrams can show covalent bonding(including double covalent bonds""
• Carbondioxide and water are simple molecules with weak intermolecular forces between molecules.
• Physical properties of carbondioxide and water related to their structure:
• As they have weak intermolecular forces they're easy to separate so the substances have low melting points.
• As they have no delocalised electrons they cannot conduct electricity
• A period are all the elements in the horizontal row.
• the period is the number of shells
• A group is all the elements in a vertical column
• The group number is the number of electrons in outer shell
• Newlands - law of octaves - elements with similar relative atomic mass appeared in the same row.
• Mendeleev - gathered evidence and put together periodic table. Left gaps for unknown elements
• How further evidence confirmed Mendeleev's ideas about the Periodic table:
• Confirmation of his prediction about unknown elements. e.g. predicted missing elements were found
• investigation on atomic structure agreed with his ideas

C4d - The group 1 elements

• Reactions with water:
• Lithium reacts quickly with water
• Sodium reacts very quickly and vigorously
• Potassium reacts extremely quickly and vigorously with water
• Their reactivity increases as you go down group( as well as density and melting points)
• Word equation
• Sodim + water >>> Sodiumhydroxide + hydrogen
• Balanced symbol equation:
• 2Na + 2H2O >>>> 2NaOH + H2
• Group 1 elements have similar properties because when they react each atom loses its outer electron to become an ion with a single positive charge.
• K - e >>> K+
• The easier it is for an atom of group 1 to lose an electron, the more reactive it is.
• The outer electron of potassium is further away from the nucleus("attractive pulling force") so it is easily lost from the atom.
• Flame tests
• What happens if you put compounds of group 1 elements in a flame:
• Lithium - Flame turns RED
• Sodium - Flame turns YELLOW
• Potassium - Flame turns Lilac
• Flame test
• Moisten a flame test wire with dilute hydrochloric acid.
• Dip the flame test wire into the sample of solid chemical
• Hold the flame test wire in a blue bunsen burner flame
• Record the colour of the flame

C4e - The group 7 elements

• Chlorine is a green gas
• Bromine is an orange liquid
• Iodine is a grey solid
• Fluorine - Lowest melting and boiling piints(gas). Displaces other group 7 elements.
• Making a metal halide:
• Lithium + Bromine >>> Lithium bromide
• 2Li + Br2 >>> 2LiBr
• Displacement reactions:
• Chlorine + potassium bromide >>> potassium chloride + bromine
• Cl2 + KBr >>> KCl + Br2
• Halogens have similar properties because when they react each atom gains one electron to from a negative ion.
• The nearer the outer shell is to the nucleus, the easier it is for an atom to gain one electon. The easier it is to gain the electron the more reactive the halogen is.
• Reduction
• Br2+ 2e >>> 2Br-

C4f - Transition metals

• Copper compounds - Blue
• Iron(II) compounds - light green
• Iron(III) compounds - Orange/Brown
• Trasnition elements and compounds used as catalytsts:
• Iron - Haber process
• Nickel - manufacturing margarine
• Thermal decompostion of metal carbonates
• Metal oxide and carbon dioxide formed
• Colour change occurs
• Symbol equation: CuCO3 >>> CuO + CO2
• Sodimhydroxide solution in transition metals:
• Cu2+ - Blue solid
• Fe2+ - Green precipitate
• Fe3+ - Orange/brown precipitate
• Cu2+ + 2OH- >>> Cu(OH)2
• Fe2+ + 2OH- >>> Fe(OH)2
• Fe3+ + 3OH >>> Fe(OH)3

C4g - Metal structure and properties

• most metals:
• are lusterous
• are hard
• have a high density
• have a high tensile strength
• have a high melting and boiling point
• are good conductors of heat
• A metallic bond is a strong electrostatic force of attraction between close-packed positive metal ions and a "sea" of delocalised electrons
• Metals have high melting and boiling points because a lot of energy is needed to overcome the stong attraction between the delocalised electrons and the positive metal ions.
• Metals conduct electriciity because of the delocalised electrons
• Superconductors are materials that conduct electricity at low tempertures with little or no resistance.
• Benefits of superconductors:
• Loss free power transmission
• Powerful electromagnets
• Super fast electronic circuits
• Drawbacks of superconductors:
• They only work at low temperatures
• Superconductors at that function at 20 *C need to be developed

C4h - Purifying and testing water

• Water used by industry is:
• A cheap raw material
• A coolant
• A solvent
• May contain some of the pollutants below:
• Nitrate (easily washed off fields by rain)
• Lead compounds(older houses have lead pipes)
• pesticide(used by farmers, wash off into river)
• Water purification process:
• Sedimentation - chemicals are added to make solid particles and bacteria settle out
• Filtration - A layer of sand on gravel filters out remaining fine particles.
• Chlorination - Chlorine is added to kill microbes
• Some soluble substances remain in the water. Some of these can be poisonous(pesticides and nitrates)
• Techniques such as distillation can be used to remove the dissolved substances in sea water. Distillation takes huge amounts of energy, so it is very expensive.
• Only used when there is not enough fresh water.
• Testing for sulphate ions
• If sulfate ions are present a white precipitate forms
• Sodium sulfate + barium chloride >>> Sodium chloride + barium sulfate
• Na2SO4 + BaCl2 >>> 2NaCl + BaSO4
• Testing for halide ions
• Chloride ions - White precipitate
• Bromide ions - Cream precipitate
• Iodide ions - Yellow precipitate
• Sodium chloride + Silver Nitrate >>> Sodium nitrate + silver chloride
• NaCl + AgNO3 >>> NaNO3 + AgCl