P4 revision

P4 revision

1. Atomic Structure

   • Sub atomic particle
     • Electrons
       • Mass = 0 Charge = -1
     • Protons
       • Mass = 1 Charge = +1
     • Neutron
       • Mass = 1 Charge = 0
   • Isotopes and ions
     • An isotope is when two of the same element have different amounts of neutrons
     • Ions are electrically charge particle formed when an atom or molecule loses or gains an electron
   • The radius of an atom is 5 × 10−10 m the radius of the nucleus is 5 x 10−15 m

2. Evolution of the atom

   • Dalton’s model
     • Thomson’s model
       • The Geiger-Marsden experiment Rutherford's theory
         • Bohr’s model
           • He improved on Rutherford's theory proving that electrons occupy shells or energy levels around the nucleus
         • They tried and experiment to prove the plum pudding model true, this experiment was
           • They aimed beams of positively-charged particles at very thin gold foil. These particles should have passed straight through, according to the plum pudding model. However, some changed direction proving the theory wrong creating the planatery model. They have 2 rules
             • atoms have a central, positively charged nucleus with most of the mass
             • electrons orbit the nucleus, like planets around a star
         • Rutherford was the scientist Geiger and Marsden were like apprentices
       • Thomson discovered the electron and created the plum pudding model his theory was
         • atoms are spheres of positive charge
         • electrons are dotted around inside
     • Dalton's model was a solid sphere that couldn't be broken down it has 4 rules
       • the atoms of a given element are identical to each other
       • the atoms of different elements are different from one another
       • during chemical reactions atoms rearrange to make different substances
       • atoms cannot be broken down into anything simpler

3. Radioactivity

   • Background radiation
     • There are many sources of background radiation, these include
       • radiation from the sun and space in general
       • from certain rocks such as granite
       • Medical equipment (x rays)
   • Half life
     • Half life is the time taken for half of the radioactive nuclei in a sample to decay to half it original size.
   • There are three ways to protect your self from radiation poisioning

4. Fission and fusion

   • Fission is the splitting ofa nuclei into two roughly of the same size daughter nuclei
     • it is used in power stations due to the amount of power it releases and ofen causes a chain reaction
       • A nutron is fired at a nucleus causing it to become unstable and splitting releasing 3 more neutrons causing three more nuclei to start reacting etc etc
       • in power stations they have movable control rods made of boron which absorb the nucleus stopping the chain reaction
   • Fusion is when two smaller nuclei join together to make a bigger heavier nuclei
     • This takes extreme heat and pressure and gives of less heat than fission due to the repelling nature of two nuclei (like magnets)

5. Types of radiation

   • Alpha
   • Gamma
   • Beta

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