Atomic structure

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    Created by
    Amelie Viney

    Cards (39)

    • How can an atom’s electron arrangement be changed?
      By absorbing electromagnetic radiation
      By Emitting electromagnetic radiation
    • Explain how an atom’s electron arrangement changed when it absorbs EM radiation:
      Electrons move further away from the nucleus
      They move to a higher energy level
    • Explain how an atom’s electron arrangement changes when it emits EM radiation:
      Electrons move closer to the nucleus
      They move to a lower energy level
    • How did the plum pudding model describe the atom?
      A ball of positive charge with negatively charged electrons distributed evenly throughout it
    • Which experiment led to the plum pudding model being discarded?
      The alpha scattering experiment
    • What is the name given to the currently accepted model of the atom?
      The Bohr nuclear model
    • State the conclusions of the alpha scattering experiment:
      Most of the mass of the atom is concentrated at the centre in the nucleus
      The nucleus is positively charged
    • What did James Chadwick’s experiments on the atom prove?
      The existence of neutrons
    • Why do unstable nuclei give out radiation?
      > Unstable nuclei undergo decay to become more stable
      > As they release radiation, their stability increases
    • What is count rate?
      The number of radioactive decays per second for a radioactive source
    • Give an example of a detector that may be used to measure count rate:
      Geiger-Muller tube
    • What are the constituents of an alpha particle?
      Two protons and two neutrons
      It is the same as a helium nucleus
    • What stops alpha radiation?
      Paper
      Skin
    • What stops beta radiation?
      A thin sheet of aluminium
      Several metres of air
    • What stops gamma radiation?
      Lead
      Concrete
    • What type of radiation is the most ionising?
      Alpha radiation
    • What type of radiation is the most penetrating?
      Gamma radiation
    • What changes to mass of charge occur due to emission of a gamma ray?
      Both mass and charge remain unchanged
    • Describe the nature of radioactive decay:
      Random
      Impossible to predict which nuclei will decay and when
    • Define the half-life of a radioactive isotope:
      The time it takes for the number of unstable nuclei in a substance to halve
    • What is radioactive contamination?

      The presence of unwanted radioactive nuclei on other materials
    • What is irradiation?

      > The process of exposing a material to nuclear radiation
      > The material does not become radioactive
    • Give 4 sources of background radiation:
      Rocks
      Cosmic rays from space
      Nuclear weapon testing
      Nuclear accidents
    • What factor determines how dangerous a particular radioactive isotope is?
      The half-life
    • Why are isotopes with long half lives particularly harmful?
      > They remain radioactive for much longer periods of time
      > They must be stored in specific ways to avoid humans and the environment from being exposed to radiation for too long
    • State 2 uses of nuclear radiation in the field of medicine:
      Examining internal organs
      Controlling and destroying unwanted tissue
    • How is radiation used in sterilisation?
      Gamma emitters are used to kill bacteria on equipment
    • Explain the process of radiotherapy:
      Gamma emitters direct gamma rays at cancerous cells
      The cancerous cells absorb the radiation and are killed
    • How are medical tracers chosen?
      > They should have a short half life and decay into a stable isotope which can be excreted
      > They should only release gamma radiation since it is weakly ionising and can easily pass though body tissue without damaging it
    • What is nuclear fission?
      The splitting of large, unstable nuclei to form smaller, more stable nuclei (+the emission of spare neutrons)
    • What usually needs to happen do induce fission?
      The unstable nuclei must absorb a neutron
    • Alongside two smaller nuclei, what else is emitted in a fission reaction?
      3 Neutrons
      Gamma rays
      Energy
    • What takes place during a chain reaction in a nuclear reactor?
      > An unstable nucleus absorbs a neutron
      The nucleus undergoes fission (splits into two smaller nuclei) and releases 3 further neutrons
      > These induce more fission which results in a chain reaction
    • What are the 3 main components of the core of a nuclear reactor?
      Fuel rods
      Control rods
      Moderator
    • What is the role of the moderator in a nuclear reactor?
      To slow down the neutrons so they are travelling at speeds which allow them to be absorbed and cause fission
    • How is the fission reaction in a fission reactor kept under control?
      > Control rods are positioned in between the fuel rods
      > The rate of fission is controlled by moving these rods
      > The lower the rods are inserted, the slower the rate of fission
    • What is nuclear fusion?
      > The joining of two lighter nuclei to produce a heavier nuclei and release energy
      > Occurs in stars
    • Name two isotopes of hydrogen which are commonly used in nuclear fusion:
      Deuterium and Tritium
    • Which releases more energy, nuclear fission or nuclear fusion?
      Nuclear fusion
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