Module C4: Chemical Patterns

Atoms
1. The Nucleus
  1. Protons and Neutrons
    1. Protons = heavy and positively charged.
      1. Elements have different numbers. All Atoms of same element have same number
    2. Neutrons = heavy and no charge
  2. Positively Charged
  3. Tiny, almost whole mass
2. The Electrons
  1. move around nucleus
  2. negetively charged
  3. No mass
  4. Arranged in Shells
  5. if added or removed atom becomes an ion (charged)
3. Number of Protons = Number of Electrons
  1. Same sized charge but opposite
Chemical Equations
1. Same atoms at start and end of reaction just rearranged
  1. Must be same amount of atoms on both sides of equation
2. Physical States
  1. (s) = solid
  2. (l) = liquid
  3. (g) gas
  4. (aq) = dissolved in water
Line Spectrums
1. Some Elements produce flames with distinctive colours
  1. Li = red flame
  2. Na = yellow/ orange flame
  3. K = lilac flame
  4. different colours in fireworks
  5. help chemists to idendity metal in compound. Burn substance, see colours produced.
2. Each Element gives a characteristic Line Spectrum
  1. If heated electrons in an atom release energy as light
    1. Wavelengths recorded as a line spectrum
  2. Different Elements = different wavelengths
    1. because of different electron arrangement
    2. Different pattern of wavelengths
      1. spectrums used to identify elements
        Spectroscopy
        scientist have discovered new elements using this eg, caesium and rubidium.
History of the Periodic Table
1. 1800s only measure relative atomic mass, elements aranged in order of this only.
  1. Dobereiner
    1. Order elements into triads (groups)
      1. based on chemical properties
  2. Newland
    1. Ordered atoms by relative atomic mass, every eigth had similar properties
      1. Newlands octives
      2. Broke down on 3rd row, he left no gaps, work was ignored.
      3. Groups contained elements that didn't have similar properties. Mixed up metals and Non-metals. No Gaps.
  3. Mendeleev
    1. 1869 arrange 50 known elements, left gaps, predicted unfound
      1. keep elements with similar properties in the same vertical groups
      2. When the element he left gaps for were discovered people believed his theory more.
    2. order of atomic mass
The Modern Periodic Table
1. Puts elements with similar properties together.
2. in order of increasing proton number
3. Metals left, none metals right (steps)
4. columns = similar properties
5. groups = vertical column
  1. group number tells you how many electrons are on the outer shell
  2. if you know properties of one element in the group you can predict the properties of other elements
6. group 1:more reactive as you go down. group 7: less reactive as you go down
Electron Shells
1. Rules.
  1. electrons occupy shells.
  2. lowest energy levels filled first
  3. 1st Shell: 2 2nd Shell: 8 3rd Shell:8
  4. most outer shells not full
    1. makes atom want to react
  5. electronic arrangement determines properties
2. Working out Electron Configurations
  1. look at the number of protons an atom has.
    1. it has the same number of electrons
      1. follow shell rules to fill up the shells for the element
Ionic Bonding
1. Ions are made when atoms lose or gain electrons
  1. can be made from single atoms or groups of atoms.
  2. they lose/ gain to try and get a full outer shell
2. Group 1 have 1 electron in outer shell.
  1. want to get rid of that one to have full shells.
    1. when they lose an electron they form positive ions
3. group 7 have outer shells almost full
  1. Want to fill them (get 1 extra electron)
    1. when they gain an electron they form negitive ions
4. Ionic compounds form a regular lattice.
  1. solid ionic compounds are made of a giant lattice of ions. each lattice forms a single crystal.
    1. When they dissolve in water they can conduct electricity because ions can move.
Group 1; The Alkali metals
1. 1 outer shell electron
2. Very reactive
  1. More violent the reation with water, the more reactive they are.
3. all similar properties
4. When they react they form similar compounds
5. shiny when freshly cut
6. react with oxygen in moist air
7. Down the group
  1. more reactive
  2. denser
  3. lower melting point
  4. lower boiling point
8. Produce Hydrogen when reacted with water
  1. fizz, some ignite
    1. reaction makes an alkaline solution
      1. a hoydroxide of the metal forms
9. Reaction with Chlorine makes salts.
  1. reacts vigorously, creates colourless crystalline salts.
Group 7: Halogens
1. 7 outer electrons
2. very reactive, create similar compounds, have similar properties
3. form diatomic molecules (always in pairs)
4. as you go down the group
  1. less reactive
  2. higher melting point
  3. higher boiling point
5. non-metals with coloured vapours
  1. Fl, very reactive poisonous yellow gas @ room temp.
  2. Cl, fairly reactive, dense green gas @room temp.
  3. Bromine, dense orange volatile liquid @room temperature and forms an orange gas
  4. Iodine, dark grey crystaline solid @room temp. or a purple vapour
6. React with alkali metals to form salts
7. They react with iron to form coloured solids called iron halides.
8. Displacement reactions, more reactive element pushes a less reactive element out.
Laboratory Safety
1. Hazard Symbols
  1. Oxidising
    1. Provides oxygen makes other materials burn more fiercely.
  2. Explosive
    1. Can explode.
  3. Highly Flammible
    1. Catches fire easily
  4. Corrosive
    1. attacks and destroys living tissues inc. eyes and skin
  5. Toxic
    1. Can cause death either by swallowing, breathing in, or absorption through the skin.

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