NUCLEAR!

• Nuclear fission


  The process in which a large nucleus is forced to split into at least two approximately equal-sized fragments with the release of neutrons and a large amount of energy

  
• Nuclear fission


  1. Used in the production of electricity in a nuclear reactor

  2. Used in nuclear weapons

  
• Most daughter nuclei of fission reactions are radioactive and will decay at a slower rate

  
• Most common fission reaction

  Single slow moving neutron bombards uranium-235 to produce uranium-236 which breaks apart into at least two similar sized nuclei, a few neutrons and a large amount of energy

  
• The energy released by nuclear fission is calculated the same way as decay reactions

  
• The amount of energy produced in nuclear fission is often more than 100 times that produced in natural radioactive decay

  
• Fission reaction


  • Uranium-235 nucleus bombarded with a single neutron fragments into three neutrons, caesium-137 and rubidium-96

  
• The energy released in the fission reaction of a uranium-235 nucleus bombarded with a single neutron is 172.6 MeV

  
• Chain reaction in nuclear fission

  • Production of extra neutrons which can go on to react with other fissile nuclei to trigger more fission reactions
  • Exponential cascade of more neutrons initiating more fission reactions

  
• The amount of material needed to sustain a chain reaction is known as the critical mass
• Nuclear fusion


  The process whereby two smaller nuclei join, or fuse, together to create a larger nucleus with the creation of energy

  
• Fusion reactions, specifically the reaction of two protons joining to make helium, are by far the most common type of nuclear or chemical reaction in the universe

  
• Conditions for nuclear fusion

  • The small nuclei must be travelling very fast (usually achieved through high temperatures - approximately 10 million degrees)
  • There need to be enough nuclei available to sustain a reaction (occurs under very high pressure)
• Common fusion reaction


  • Reaction of deuterium and proton to form helium-3

  
• The amount of energy released in the fusion reaction of deuterium and proton to form helium-3 is 4.98 MeV

  
• The energy per mass of reactants is much higher in nuclear fusion compared to nuclear fission
• Atom


  The basic building block of all matter
• Nucleus of an atom

  • Consists of positively charged protons and neutral neutrons, surrounded by much lighter negatively charged electrons

  
• Protons


  Have a positive charge and a mass almost 2000 times the mass of an electron. The number of protons in the nucleus of the atom determines the element.
• Neutrons


  Have no charge hence they are neutral
• Electrons


  Have a negative charge and are significantly smaller than protons and neutrons
• Properties of the 3 major particles found in atoms

  • Particle
  • Location
  • Symbol
  • Charge (C)
  • Mass (kg)
  • Mass (u)

  
• Nucleons


  Protons and neutrons that comprise the nucleus

  
• Nuclide


  The nucleus made up of protons and neutrons

  
• Atomic number (Z)


  The number of protons in a nucleus

  
• Mass number (A)


  The sum of the number of protons and neutrons in a nucleus
• Nuclear notation


  1. X_Z^A

  2. Element symbol

  3. Atomic number

  4. Mass number

  
• There are 250 stable nuclei that exist in nature. Pb-208 is the heaviest naturally occurring stable nuclide.
• Stable nucleus


  A nucleus that does not gain or lose any protons, neutrons or energy over time
• The periodic table indicates, in yellow, all elements that have no stable isotopes.

  
• Radioactive


  An unstable nucleus that changes over time, or has an excess of energy
• Radioisotope


  A radioactive isotope
• Radionuclide


  An unstable nucleus
• Coulomb/Electrostatic force


  The force acting on charged particles that causes them to move
• In a nucleus, there is no Coulomb force between 2 neutrons or between a neutron and a proton because neutrons have no charge.
• Strong nuclear force (SNF)


  The force that overcomes the repulsive electrostatic forces to hold the nucleus together
• The strong nuclear force is one of the four fundamental forces that exist in the universe, the others being electromagnetic, gravity and weak nuclear force.
• Strong nuclear force


  • Mainly attractive, acts only in the nucleus on protons and neutrons, and acts at only very short distances
• If more protons are added to a nucleus

  More neutrons must be added for the SNF to balance the Coulomb force
• Radioactive nuclides occur where

  There are either too many protons relative to the number of neutrons (resulting in β+ decay) or there are too many neutrons relative to the number of protons (resulting in β- decay)