Elements of life

Atomic Models
1. 1 .John Dalton theory of solid sphere's
2. 2.JJ Thompson concluded Positively charged sphere with negative electrons embeded Plum pudding.
3. 3. Rutherford Positive nucleus , cloud of negative electrons , empty space.
4. 3.Further research (neutron- James Chadwick)
5. 4.Bohr model - Improvement Spiral down and collapse. 4 rules Fixed frequency. Present.
Relative Mass.
1. Relative masses are masses of atoms compared to Carbon 12.
2. Relative masses can be using a mass spectrometer. Method is called Mass spectorscopy.
  1. Mass spectrometer consists of 4 stages: Vaporisation , Ionisation , acceleration , detection.
    1. Vaporisation : sample is turned into gass using electrical heater.
    2. Ionisation: Gas particles are bombarded with high energy electrons. electrons are knocked of the particles turning them posi ions.
    3. Accleration: Posi ions are accelrated by an eletric field.Given the same kinectic energy.
    4. Detection: Time taken to reach the detector is measured. Depends on the ions mass and charge- light highly charged ions will reah first and the oppisite after.
    5. After each sample is analysed a mass spectrum is produced.
      1. Mass specturm Y axis = abundance X axis = Mass charge ratio.
3. Mass spectrometry can be used to find Mr. But bombarding molecules with electrons causes them to break into fragments .This will show on the MS making a fragmentation pattern. These can be used to indentify molecules and their structure.
Nuclear Radiation.
1. Alpha - Strong ionising ability - slight deflection in electric field.
2. Beta-Moderate ionising ability - large deflection in electric field.
3. Radioactive dating.
  1. Invovles measuring how much a Particular carbon there is in plant remains ect.
  2. All living things have the same % of C14 But as they die tthe % begins to decrease as C14 decays. Less % older it must be. Approx age.
Shell's & Atomic Spectra
1. Shell 3-Max 18 electrons Shell 4-Max 32 electrons
  1. 3&4shells overlap. even if the 3rd shell isnt full electrons go on 4th shell. then it goes back to filling 4th Shell.
2. Energy is related to frequency: when an electron absprbs or emmits ER with certain Freqeunces the amount of energy emiited or absorbed is related to the frequency by ^e=hv
3. Always frequency X planks constant for energy!
Bonding.
1. Ionic
  1. Between metal and non-metal.
  2. Ionic compounds.
    1. Conduct electricity when molten or dissolved but not when solid.
      1. ions in liquid are free to move but in solid they are fixed by strong ionic bonds.
    2. High boiling and melting points.
      1. Strong electrostatic forces. Takes a lot of energy.
    3. Often dissolve in water.
      1. Water is polar pull away ions away from lattice with their poistive and negative ends.
2. Covalent
  1. between to non-metals.
  2. Dative is where both electrons come from one atom
  3. Fairly low boiling points. no giant strcuture
  4. Dont conduct Ele no charge carriers
  5. Insoluble polar are vain so leave them alone.
3. Metallic
  1. Two metals.
  2. High melting point strong metallic bonding
  3. Thermal conductors free ele
  4. insoluble strong metallic bonds.
Shapes of molecues.
1. Electrons repeal each other as far as possible creating angles and shapes.
  1. 2 Pairs = 180=linear
    1. 3pairs-No lone = 120 =Trigonal planar
      1. 3 pairs 1 lone = 120 = bent
        4pairs=109=tetrahedral
        4pairs 1 lone=109=trigonal pyramidal
        5pairs-120/90=trigonal bipyramidal
        6pairs=90=octahedral
Group 2
1. Soulubility of hydroxide increases down the group.
2. carbonate soulubilty decreases as you go down the group.
Periodic Table.
1. Pattern's
  1. simple molecular
    1. MP Depends on intermolecular forces.
  2. Giant covalent strcuture
    1. Gaint cocalent highest melting eg Si and carbon
  3. Metals melting and boiling points increase across.
    1. due to increase number of electrons decreasing radius higher denisity.
6.02x10^23 avogardo's constant.

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