Atomic structure

  • Created by: holly6901
  • Created on: 28-03-19 16:06
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  • Atomic structure
    • Developing the model of the atom
      • General stuff
        • New models change when new evidence is found that can't be explained by the old model
        • Scientists used to think atoms were solid balls until they discovered electrons
        • This led to the plum pudding model
      • The plum pudding model
        • The plum pudding model showed the atom as a ball of positive charge with electrons scattered in it
        • Later, scientists fired alpha particles at gold foil and proved the plum pudding model wrong
      • The nuclear model
        • Invented by Neils Bohr
        • Electrons go around the nucleus in shells
        • Each shell is a fixed distance from the nucleus
        • Bohr's theory was proved correct by many experiments
      • James Chadwick's experiments proved neutrons exist
      • The current model of the atom
        • The radius of an atom is about 1x10 to the power of -10
        • The nucleus is tiny but takes up most of the mass of the atom
        • The radius of the nucleus is 10,000 times smaller than the radius of the atom
        • The nucleus is made of protons and neutrons
        • Protons are positively charged and neutrons have no time
        • Electrons orbit the nucleus at different distances. These distances are called electron shells
        • Atoms overall have a neutral charge
      • Electrons have more charge, the further away from the nucleus they are. Electrons can move energy shells by absorbing electromagnetic radiation.
    • Isotopes
      • Atoms of the same element  have the same number of protons
        • The atomic number shows the number of protons whereas the mass number shows protons+neutrons
      • Isotopes are atoms with the same number of protons but a different number of neutrons
      • Some isotopes emit radiation from their nuclei to become more stable. This is radioactive decay
      • Isotopes that emit radiation are called radioactive isotopes
    • Untitled
    • Types of nuclear radiation
      • Alpha
        • Strong ionising power
        • Range of a few centimetres
        • Stopped by a sheet of paper
      • Beta
        • Moderate ionising power
        • Range of a few metres
        • Stopped by a sheet of aluminium
      • Gamma
        • Weak ionising power
        • Range of a long distance
        • Stopped by a thick sheet of lead or metres of concrete
      • Neutrons
        • Isotopes can also give out neutrons when they decay
      • Ionising radiation turns atoms into ions. The ionising power is how easily types of radiation can do this.
    • Nuclear equations
      • Nuclear equations are usually written as nucleus before decay-> nucleus after decay + radiation emitted
      • The total mass and atomic numbers must be equal on both sides of the arrow
      • When a nucleus emits an alpha particle, its atomic number decreases by 2 and its mass number decreases by 4
      • In beta decay its atomic number increases by 1 and its mass number stays the same
      • In gamma decay, both the atomic number and the mass don't change
    • Half-life

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