Nuclear physics

• what is the structure and size of an atom

  positively charged nucleus 1x10^-14m

  with shells of negative electrons orbiting it

  atom = 1x10^-10m
• what affects the electron arrangement in an atom?

  Electrons are in shells at different energy level

  when they absorb EM radiation they go up shells

  when they emit EM radiation they do down shells
• what is mass number

  Protons + neutrons
• What is atomic number

  proton number
• what is an isotope

  An Atom with the same number of protons but a different number of neutrons
• why is a scientific model or theory changed

  there is new evidence that doesn’t fit the current model
• what was the plum pudding model

  the atom Is a ball of positive charge with negative electrons embedded in it
• what were the discoveries of the alpha scattering experiment

  fired alpha particles at thin gold foil

  most went straight through the atom is mostly empty space

  some deflected showing the atom has a positive nucleus where mass is concentrated
• what did Bohr discover

  Electrons orbit the nucleus in shells at specific distances from the nucleus
• What was discovered after Bohrs discovery

  The proton
• what did Chadwick discover

  The neutron which lead to understanding of isotopes
• what is activity and how is it measure

  activity is the decay of an unstable nucleus measure in bequerels (Bq)
• What is count rate how is it measured

  the number of decays per second

  measured using a Geiger muller tube
• what are the types of nuclear radiation

  Alpha(α)- most ionising, least penetrating (only stopped by paper, can only move a few cm in air)

  Beta(β)- middle ionising, middle penetrating (stoped by 3mm aluminium, moves 1m in air)

  Gamma(γ)-low ionising, highest penetrating(stopped by thick lead and concrete, can move kilometres in air)
• what is a half life (the equation)

  The time taken for the count rate of a radioactive material to half

  number of decayed = initial number x 0.5^half lives
• why do we use half lives

  radioactive decay is random and spontaneous so a half life is like an average
• what is contamination

  why is it a hazard

  what are the uses

  when an object has radioactive material on it

  hazard- ionising cells

  used for medical tracers and to check for leaks in pipes
• What is irradiation

  what are the hazards

  what are the uses

  when an object is exposed to radiation

  hazard- ionising cells

  used to kill cancer
• what are the sources of background radiation

  Radon gas

  medicine

  nuclear weapons test

  nuclear power plants

  cosmic rays
• Describe the nature of radioactive decay

  Random and spontaneous
• what are the uses of radiation

  alpha - smoke detectors

  beta - medicine

  gamma - medical tracers, gamma knife, sterilisation
• how to reduce the hazard of radiation

  Distance

  shielding (lead apron, ppe)

  Limit time
• what is the importance of pear review

  check for bias and inaccuracy

  other scientist can learn from findings and improve it
• How is radiation dose measured

  Sieverts
• What is the process of nuclear fission in A nuclear reactor

  nuclear fuel is held in rods

  when triggered a neutron is fired at the fuel

  the neutron is absorbes causing the nucleus to split into 2

  2 or 3 neutron and gamma rays are released

  the neutrons are absorbed by other nuclei forming a chain reaction
• how is fission in a reactor different to in a nuclear bomb

  fission in a reactor is controlled by control rods which absorb neutrons to slow down the chain reactions
• what is nuclear fusion

  when 2 small nuclei collide to form 1 larger nucleus

  some mass is converted to energy