Elements of life

Elements of life

1. Atomic Models

   • 1 .John Dalton theory of solid sphere's
   • 2.JJ Thompson concluded Positively charged sphere with negative electrons embeded Plum pudding.
   • 3. Rutherford Positive nucleus , cloud of negative electrons , empty space.
   • 3.Further research (neutron- James Chadwick)
   • 4.Bohr model - Improvement Spiral down and collapse. 4 rules Fixed frequency. Present.

2. Relative Mass.

   • Relative masses are masses of atoms compared to Carbon 12.
   • Relative masses can be using a mass spectrometer. Method is called Mass spectorscopy.
     • Mass spectrometer consists of 4 stages: Vaporisation , Ionisation , acceleration , detection.
       • Vaporisation : sample is turned into gass using electrical heater.
       • Ionisation: Gas particles are bombarded with high energy electrons. electrons are knocked of the particles turning them posi ions.
       • Accleration: Posi ions are accelrated by an eletric field.Given the same kinectic energy.
       • 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.
       • After each sample is analysed a mass spectrum is produced.
         • Mass specturm Y axis = abundance X axis = Mass charge ratio.
   • 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.

3. Nuclear Radiation.

   • Alpha - Strong ionising ability - slight deflection in electric field.
   • Beta-Moderate ionising ability - large deflection in electric field.
   • Radioactive dating.
     • Invovles measuring how much a Particular carbon there is in plant remains ect.
     • 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.

4. Shell's & Atomic Spectra

   • Shell 3-Max 18 electrons Shell 4-Max 32 electrons
     • 3&4shells overlap. even if the 3rd shell isnt full electrons go on 4th shell. then it goes back to filling 4th Shell.
   • 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
   • Always frequency X planks constant for energy!

5. Bonding.

   • Ionic
     • Between metal and non-metal.
     • Ionic compounds.
       • Conduct electricity when molten or dissolved but not when solid.
         • ions in liquid are free to move but in solid they are fixed by strong ionic bonds.
       • High boiling and melting points.
         • Strong electrostatic forces. Takes a lot of energy.
       • Often dissolve in water.
         • Water is polar pull away ions away from lattice with their poistive and negative ends.
   • Covalent
     • between to non-metals.
     • Dative is where both electrons come from one atom
     • Fairly low boiling points. no giant strcuture
     • Dont conduct Ele no charge carriers
     • Insoluble polar are vain so leave them alone.
   • Metallic
     • Two metals.
     • High melting point strong metallic bonding
     • Thermal conductors free ele
     • insoluble strong metallic bonds.

6. Shapes of molecues.

   • Electrons repeal each other as far as possible creating angles and shapes.
     • 2 Pairs = 180=linear
       • 3pairs-No lone = 120 =Trigonal planar
         • 3 pairs 1 lone = 120 = bent
           • 4pairs=109=tetrahedral
             • 4pairs 1 lone=109=trigonal pyramidal
               • 5pairs-120/90=trigonal bipyramidal
                 • 6pairs=90=octahedral

7. Group 2

   • Soulubility of hydroxide increases down the group.
   • carbonate soulubilty decreases as you go down the group.

8. Periodic Table.

   • Pattern's
     • simple molecular
       • MP Depends on intermolecular forces.
     • Giant covalent strcuture
       • Gaint cocalent highest melting eg Si and carbon
     • Metals melting and boiling points increase across.
       • due to increase number of electrons decreasing radius higher denisity.

9. 6.02x10^23 avogardo's constant.

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