P1.1 - The particle model

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Created by
Lavinia C

Cards (16)

  • Atom
    Smaller, negatively charged particles called electrons
  • Plum pudding model (or JJ Thomson's model)

    Negative electrons spread through the positive 'pudding' that made up most of the atom
  • Gold foil experiment
    1. Fired positively charged alpha particles at an extremely thin sheet of gold
    2. Most particles went straight through or were slightly deflected
    3. Some were deflected more than expected, a few were deflected back the way they had come
  • Nuclear atom model
    Most of the mass of an atom is concentrated in a tiny, positively charged nucleus at the centre, surrounded by a 'cloud' of negative electrons
  • Electrons in a 'cloud' around the nucleus would be attracted to the nucleus, causing the atom to collapse.
  • Bohr model
    Electrons can only exist in fixed shells (or orbits), and not anywhere in-between. Each shell has a fixed energy
  • Subatomic particles
    • Protons
    • Neutrons
    • Electrons
  • Nucleus
    • Contains protons and neutrons
    • Gives the nucleus an overall positive charge
    • Tiny - nuclear radius is about 1 x 10^-15m
    • Almost the whole mass of the atom (about 1 x 10^-23 g) is concentrated in the nucleus
  • Atom

    • Mostly empty space
    • Negative electrons whizz round outside the nucleus really quickly, in electron shells
    • Gives the atom its overall size - the diameter of an atom is around 1 x 10^-10 m
  • Molecule
    Atoms joined together
  • Subatomic particle properties
    • Protons: relative mass 1, relative charge +1
    • Neutrons: relative mass 1, relative charge 0
    • Electrons: relative mass 0.0005, relative charge -1
  • Density
    Measure of the 'compactness' of a substance, relates the mass of a substance to how much space it takes up
  • Density = mass / volume
  • The density of an object depends on what it's made of, not its size or shape
  • The average density of an object determines whether it floats or sinks
  • Measuring the density of solids and liquids
    1. Measure the mass and volume of a sample
    2. Use the formula density = mass ÷ volume