C4 - The Periodic Table

Atomic Struture
1. Protons: positively charged, charge +1, mass 1
2. Neutrons: no relative charge, charge 0, mass 1.
3. Electrons are negatively charged, charge -1, mass 0.0005
4. Atomic Number = number of protons element contains found at the bottom of element on P.T
5. Mass Number = total number of protons and neutrons element contains
6. Isotopes = same element, same atomic number, different mass number.
Electronic Structure
1. Compound = two or more elements, chemically combined.
2. Chemical formula = symbols of all elements in a compound and number of atoms of each element.
3. Electrons occupy shells around the nucleus
  1. first shell can home two electrons.
  2. second and third shells can home up to eight electrons
Ionic Bonding
1. If an atom loses one or more electrons it becomes a positively charged ion
  1. Hydrogen and metal atoms
2. If an atom gains one or more electrons it becomes a negatively charged ion
  1. Non-metal atoms
3. Metal reacts with non-metal
  1. Electrons transferred from metal to non-metal
    1. Positive metal ions attract negative non-metal ions and form ionic bonds.
      1. Dot and cross diagrams
Ionic Compounds
1. Giant ionic lattice
  1. Structure repeated many times
  2. Positive ions strongly attracted to negative ions.
2. Ionic bonds need a lot of energy to be broken
  1. High Melting Point.
  2. Can conduct electricity in a molten or liquid solution - ions are free to move around
Periodic Table
1. horizontal rows = period
2. vertical column = group
  1. Elements in a group have similar properties
3. number of electron shells occupied = period element is found
  1. Number of electrons in outer shell = group number
Covalent Bonding
1. two non-metals
2. Shared pair of electrons
3. Each covalent bond is shown as a straight line in displayed formula
4. Weak intermolecular forces
5. Low melting point
6. Does not conduct electricity
7. Shared electrons shown on diagram in shared area between atoms
Group One Elements
1. React vigorously with water to form alkaline solutions
  1. Stored in oil to keep them away from water and air
2. Metal + Water = Metal Hydroxide + Hydrogen
  1. 2M + 2H20 = 2MOH + H2
3. reactivity increases as you go down the group.
4. In water, lithium keeps its shape, potassium and sodium melt and form silver balls
  1. Potassium ignites explosively and burns with a lilac flame
    1. Lithium disappears slowly, sodium disappears quickly and potassium disappears very quickly
5. Each have one electron in outer shell
6. Loss of electron = oxidation
  1. M = (M+) + (e-)
7. Densities increase as you go down the group
8. Melting points increase as you go down the group
Flame Tests
1. Lithium burns red
2. Sodium burns orange
  1. Potassium burns lilac
Group Seven Elements
1. Halogens - react with metal to make salts
  1. Chlorine sterilises pools and tap water
  2. Iodine is used as antiseptic on wounds
2. Chlorine is a green gas
  1. Group Seven elements react vigorously with Group One
    1. Metal Halide clouds produced
    2. 2M + X2 = 2MX (where M = group one and X = group 7)
3. Bromine is an orange liquid
4. Iodine is a grey solid
Displacement reactions
1. A more reactive group 7 will displace a less reactive group 7 from its metal hallide.
  1. X2 + 2MY = Y2 + 2MX where X = group 7 and MY = metal hallide
    1. Gain of electron = reduction
      1. X2 + (2e-) = 2X-)
Transition Elements
1. between groups 2 and 3
  1. They are all metals
    1. Strong, malleable and shiny when cut
2. Copper compounds are often blue
3. Iron(II) compounds are often light green
  1. Iron(III) compounds are often orangey brown
    1. Often used as catalysts, EG: iron is used in the haber process.
    2. Thermal Decomposition = substance breaks down to form two or more substances when heated
      1. Metal carbonate = metal oxide + carbon dioxide
        Normally causes a colour change
Precipitation reactions
1. Copper(II) - blue metal hydroxide precipitate
  1. Iron (II) - grey/green metal hydroxide precipitate
    1. Iron (III) - orange/brown metal hydroxide precipitate
Metal
1. Good conductor of electricity
  1. hard, lustrous, malleable and have tensile strength
2. Metallic bonding - strong - high melting and boiling points
  1. Closely packed ions
  2. sea of delocalised electrons
    1. Takes a lot of energy to overcome bonds
Water Purification
1. Water comes from underground aquifers, resevoirs, lakes and rivers.
  1. contains many dissolved substances which need to be removed
2. Water can be used in industry as a solvent, a coolant or a cheap raw material
  1. Sulfate ions can be detected by barium chloride solution
    1. Sample of water in test tube, barium chloride added
      1. Sulfate Ions present = white precipitate
        Na2SO4 + BaCl2 = 2NaCl + BaSO4
  2. Hallide ions can be detected by silver nitrate
    1. Chloride Ions = White precipitate
    2. bromide ions = cream precipitate
      1. NaCl + AgNO3 = NaNO3 + AgCl
    3. iodide ions = pale yellow precipitate
3. Only 3% of the Earth's water is fresh
  1. Pollutants in water = nitrates, lead compounds and pesticides
    1. Distillation can make pure water from sea water but requires lots of energy and is more expensive
  2. Large suspended particles removed by sedimentation
    1. Small suspended particles removed by filtration
      1. chlorination kills microbes in the water

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