Nuclear Physics

• J.J. Thomoson developed the 'Plum Pudding' Model
• The 'Plum Pudding' model proposed that atoms were positively charged masses with electrons embedded inside them.
• Rutherford's Finding #1

  Most of the alpha particles passed through unaffected therefore the atom is largely empty space and most of its matter is concentrated in a space much smaller than the atom.
• Rutherford's Finding #2

  Some alpha particles deviated at large angles, so these alpha particles must have experience a repulsive force from a nearby concentration of positive charge. The positive charge is concentrated in this small mass within the atom.
• Rutherford's Finding #3

  Around 1/8000 alpha particles deflected by more than 90 degrees. These alpha particles must have collided into something much more massive than an alpha particle.
• Nuclear reactions are when protons and neutrons rearrange.
• The three types of nuclear reactions are: fission, fusion, and decay.
• A nuclide is a distinct atom/nucleus determined by its specific number of protons and neutrons.
• A nuclide will be unstable when it has too few neutrons, too many neutrons, or too much energy.
• An unstable nuclide (parent nuclide) will emit radiation to form a daughter nuclide that is more stable. The daughter nuclide and radiations are called decay products.
• Beta decay is when a neutron decays to form a proton and releases a beta particle (electron). Beta particles travel at the speed of light.
• An alpha particle is a helium nucleus that has two protons and two neutrons.
• Gamma particles are called photons. Gamma rays are an electromagnetic wave so they travel at the speed of light.
• Background radiation is the radiation that naturally arises from cosmic rays or isotopes in soil and the air or medical rests for example.
• An absorber is a material that prevents radiation from passing through it.
• Activity is the number of radioactive emissions/counts per second
• Alpha emission is the release of Alpha particles from unstable heavy nucleus
• An alpha particle is a nucleus of a Helium atom (2 protons + 2 neutrons)
• An atom is a single unit of an element that can exist
• Becquerel is the unit for measuring radiation (the number of 'counts' per second)
• Beta emission is when a neutron coverts to a proton in the nucleus, emitting an electron
• A beta particle is a high energy (fast moving) electron that is emitted from the nucleus during beta decay.
• Cathode rays are negatively charged particles (electrons) that are emitted from the negative terminal (cathode) of a vacuum glass tube.
• A cell mutation is a change in the function of a living cell that can be caused by ionising radiation.
• A chain reaction is a self sustaining reaction where some of the products are able to produce more reactions of the same kind (e.g. nuclear fission)
• Control rods are used to slow down the rate of nuclear fission in a nuclear power station.
• Controlled nuclear fission is the slow and steady production of nuclear power
• Dalton's model: Each element is made up of indivisible parts called atoms. All atoms of the same element are identical.
• A gamma emission/ray is a high energy electromagnetic wave that is emitted from unstable nuclei
• A Geiger counter is a device used to measure the radioactivity of different materials.
• Half life is the time taken for half the isotopes in a radioactive sample to decay.
• Ionisation is the ability of a nuclear radiation to remove an electron off an atom, making it an ion.
• Nuclear fission is the splitting of a larger unstable nucleus into two more stable ones, releasing energy.
• Nuclear fusion is a nuclear reaction joining two smaller nuclei to make a bigger nucleus.
• A nuclear reactor is a steel vessel in which controlled nuclear reactions take place, releasing heat energy.
• Nucleons are particles that exist in a nucleus (protons or neutrons)
• Zinc sulphide is a material that flashes when radiation hits it.
• John Dalton discovered that:

  -All matter is made up of atoms

  -Atoms of a particular element all have the same properties

  -Atoms of different elements have different properties
• J.J. Thompson discovered:

  -The 'Plum Pudding Model'

  -Electrons
• Rutherford discovered:

  -An atom is made up of mostly empty space

  -The nucleus is a positively charged mass located in the centre of an atom