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Structure of the Atom, Stoke's Law and Millikan's Experiment,…

- - - - Viscous Drag Force (N)
        
        Increased by
        
        viscosity
        
        radius
        
        velocity
        
        Constant
        
        viscosity of the fluid
        
        r
        
        radius of the object (m)
        
        v
        
        velocity of the object
- - - - weight force
        
        acts downwards
      - viscous drag force
        
        acting upwards
        
        due to air
    - - when acceleration = 0
        
        weight force = viscous drag force
        
        radius of oil drop
        
        mass = volume x density
        
        drop is a sphere
      - no net force acts on dro p
  - - - Applicable
        
        weight force
        
        acts downwards
        
        electric force
        
        Equate
        
        substitute radius
        
        mean he can find the charge of any oil drop that fell in the field
      - viscous drag force = 0
        
        acting upwards
        
        due to air
- - - - power source on
        
        potential difference applied between the opposite plates
        
        creates an electric field
        
        exerts a force on the oil drops
    - - creates fine mist of oil drop
        
        fell through a hole in the plate
        
        observed through a microscope
        
        microscope had scale
        
        measures distance then calculate velocity
- - - - Quantised Charge
        
        when the charge of any object exists in packets of a particular size
      - size on an electron
    - - had mass
      - has charge
- - - - Neutrons
        
        Middle of atom
        
        Make up nucleus
      - Electrons
        
        Orbit the nucleus
        
        Orbit is much bigger than nucleus
      - Protons
        
        Middle of atom
        
        Make up nucleus
- - - - Mass
      - Charge
        
        Positve
      - Element
        
        Determined by no. of protons
        
        1
        
        Hydrogen
        
        10
        
        Neon
        
        100
        
        Fermium
      - Smaller than atoms
    - - Mass
      - neutral particles
      - same amount of protons and electrons
    - - Mass
      - Charge
        
        Negative
      - kept in orbit by positively charged protons
  - - - Looking at masses and charges relative to others in the atom
    - - Protons
        
        Relative charge of 1
        
        relative mass of 1kg
      - Neutron
        
        relative mass of 1
        
        relative charge of 0
      - Electron
        
        relative mass of 0.0005
        
        relative charge of -1
- - - - Replace it with element symbol
    - - Proton Number
      - Atomic Number
    - - Nucleon / Mass Numebr
    - - Subtract nucleons from protons
        
        A -Z
  - - - Element with same number of protons but different number of neutrons
- - - - same as charge of an electron
- - - - Simply
        
        Mass of an carbon atom divided by 12 will produce atomic mass unit
      - one twelfth of the mass of an unbound neutral atom of carbon-12 in its nuclear and electronic ground state
- - - - result of potential difference applied to cathode
    - - Electron Beam
  - - - Used to observe internal environment
    - - As much gas as possible is removed
        
        Makes it into a vacuum
      - When cathode rays are fired across the tube they'll make it to the end of the tube
      - If not evacuated
        
        hence leaving a lot of gas in the tube
        
        The electrons would collide with all the gas particles in the tube
      - Minimises cathode ray collisions
  - - - Giving off charged particles by heating
    - - The free electrons gain kinetic energy
        
        if enough energy is gained electrons can break free from metal's surface
    - - Power Gun
        
        Supplies high potential difference
      - Anode
        
        Positively charged metal
        
        hole in the center
        
        allows beam of electrons through into further parts of the tube
        
        once through it's exposed to further manipulation of electron beam
        
        by electric and magnetic fields
      - sets up a strong electric field
        
        the electrons want to leave the negatively charged cathode and go to the positive anode
        
        Once they leave the cathode they accelerate towards the anode's electric field
        
        Some hit the cathode while others hit the glass tube
        
        Causing fluorescence
        
        High speed collision excites electron wihtin glass to higher energy levels
        
        We give the electrons the energy to carry this out by heating up the cathode
- - - - when placed in electric and magnetic fields rays deflected
    - - Creating fluorescence
    - - if anode turned into maltese cross
        
        shadow of cross is directly behing it on the wall of the cathode ray tube
    - - when a glass wheel is in the path of the rays
        
        The wheel is observed to turn across its tracks
        
        due to being pushed by the rays
  - - - otherwise we wouldn't see the shadow
    - - therefore has mass
    - - facilitated the discovery of the first subatomic particle
        
        the atom
- - - - Electron
        
        force on electron creates downward inflection
        
        Downward deflection causes the electron to undergo circular motion
        
        Motion can be described through centripetal force
        
        Equations for force on electron
        
        q = e
        
        charge on an electron
        
        Equate two equations
        
        Rearranged
        
        3 more items...
      - Magnetic Field
        
        charged objects moving through a magnetic field experience a force
- - - - Two parallel electric plates in one axis
        
        A magnetic field in the other
      - Source of cathode rays
      - Two coulometer slits
        
        A stopper with a thin gap
        
        It'll make make the rays into a thin beam
      - Fluorescent screen
        
        that'll leave a visible mark when hit by the stream of electrons
  - - - adjust the field of each of them
        
        do it until an undeflected path is created
        
        The two fields act on opposite directions on the particle
        
        electron will only make it through undeflected if the two forces are equal
        
        Equate two equations
        
        1 more item...
    - - observed deflection of particle from unopposed magnetic field
        
        using fluorescent screen radius of deflection can be measured through using a rule
        
        Equate
- - - - Outline
        
        Alpha particles were fired at a thin metal foil sheet
        
        Observed how particles interacted with foil
        
        Knew that metal foil was made up of atoms
        
        Didn't know structure of atoms
        
        Thought it was a sphere of positive charge with negative electrons floating inside
        
        called Thomson's plum pudding model
        
        Revised Outline
        
        Those scattered moved in a variety of directions
        
        Many particles passed right through foil
      - Results
        
        Expectation
        
        because the atom lacked solid mass it was assumed the alpha particles would not collide anything and pass straight through
        
        Assumed no major deflections
        
        Many passed straight through as expected
        
        some deflected in crazy directions
        
        Such as
        
        right angles
        
        Right back at source
        
        Rutherford Scattering
        
        Occurs when alpha particles are scattered in variety of angles by an atom
        
        invalidated plum pudding model
      - Implications
        
        The atom must be a lot of empty space
        
        Whatever is there must be small and very dense
        
        The dense part should be positively charged
  - - - Atom is made up of a lot of empty space
      - Middle is nucleus
        
        Dense positive charge
      - Orbiting around the nucleus are electrons
    - - Many pass through the atom
        
        However, those that don't are deflected off the nucleus
- - - - Knew that there were protons yet had no knowledge about anything else
        
        These other elements were Neutrons
    - - Same size and mass of a proton
      - Have no charge
        
        neutral
  - - - They bombarded beryllium with alpha particles
        
        this produced radiation
        
        radiation had energy of 10MeV
        
        highly penetrating radiation
        
        assumed it was gamma rays
        
        energy was more than any observed gamma ray
    - - Aimed radiation produced by beryllium at paraffin wax
        
        knocked protons out of the wax
        
        protons had an energy of approx 5 mega electron volts
  - - - James Chadwick looked at the energy of the knocked out protons
        
        If energy was gamma rays it protons would've been 50MeV
        
        Identified this through
        
        Conversation of Energy
        
        Conservation of Momentum