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P4 - Atomic Structure (Half-life (The radioactivity of a source decreases…

- - - - 1 Bq = 1 decay per second
- - - - If they gain energy by absorbing EM radiation they move to a higher energy level, further from the nucleus
      - If one or more outer electrons leave the atom, the atom becomes a positively charged ion
- - - - Radioactivity of naturally occurring unstable isotopes (in the air/food/building materials/rocks)
      - Radiation from space - cosmic rays. They mostly come from the sun however the Earth's atmosphere protects us from most of this
      - Radiation due to human activity (eg. fallout from nuclear explosions/nuclear waste - this represents a tiny proportion of background radiation)
  - - - Objects near a radioactive source are irradiated by it
      - We're always being irradiated by background radiation sources
    - - Standing behind barriers/being in a different room
      - Keeping sources in a lead-lined box
      - Using remote-controlled arms
  - - - Industrial workers should wear protective suits to stop them breathing in particles
      - Wear gloves and tongs when handling sources to avoid particles getting stuck to your skin/under your nails
  - - - Alpha is the most dangerous
        
        Gamma is the least danergous as most will pass straight out - they are the least ionising
        
        Beta is less damaging as radiation is absorbed over a wider area, and some passes out of the body altogether
        
        Do all their damage in a very localised area (very ionising)
    - - Beta and gamma are the most dangerous
        
        They can penetrate the body and damage organs
        
        Alpha isn't penetrating so is less dangerous
        
        High levels of irradiation from all sources is dangerous, but especially from beta/gamma
    - - This is why it is important research is published
      - Data is peer-reviewed and can quickly become accepted
      - The more we understand how radiation affects our bodies, the better we can protect ourselves
      - This results in improvements in our use of radioactive sources
- - - - Smoke detectors
        
        It ionises air particles causing a current to flow. If there is smoke in the air, it binds to the ions - the current stops and the alarm sounds
  - - - Test the thickness of sheets of metal
        
        As the particles are not immediately absorbed by the material (like alpha) and don't penetrate as far (like gamma)
        
        You can test leaks in pipes (if there isn't a leak you won't detect any beta but if there is the beta radiation will pass through and the detector will recognise it)
  - - - In nuclear equations, an alpha particle can be written as a helium nucleus
      - eg. Uranium-238 = Thorium-234 + Alpha particle
      - Decreases the charge and mass of the nucleus
        
        The atomic number reduces by 2
        The mass number reduces by 4 #
        
        The charge of the nucleus decreases (less positive)
    - - Increases the atomic number and charge of the nucleus
        
        The atomic number increases by 1
        The mass number stays the same as a proton is gained by a neutron is lost
        
        The charge of the nucleus increases (more positive)
      - eg. Carbon-14 = Nitrogen-14 + Beta particle
    - - Don't change the charge or mass of the nucleus
      - Are a way of getting rid of excess energy from a nucleus
- - - - This can cause radiation sickness (leading to vomiting, tiredness & hair loss) if lots of cells are killed at once
    - - This can give rise to mutant cells which divide uncontrollably - CANCER
    - - Can lead to tissue damage
  - - - Gamma isotopes are used (never alpha) so that the radiation passes out of the body without causing much ionisation
        
        They should have a short half-life so the radioactivity inside the patient quickly disappears
      - eg. Iodine-123 is absorbed by the thyroid gland just like normal iodine-127,
        
        But it gives out radiation which can be detected to indicate whether the thyroid gland is taking in iodine as it should
      - Radioactive isotopes can be injected/swallowed by people and their process around the body can be followed by an external detector
        
        A computer converts the reading to a display which shows where the strongest reading is coming from
    - - Gamma rays are directed carefully and at just the right dosage to kill the caner cells without damaging too many normal cells
        
        Radiation-emitting implants (usually beta-emitters) can also be put next to/inside tumours
      - A fair bit of damage is inevitably done to normal cells
        
        This causes the patient to be very ill
        
        If the caner is successfully killed off, it's worth it though
      - High doses of radiation will kill living cells, it can be used to treat cancers #
  - - - Many people chose to have radiotherapy as it may completely get rid of their cancer - the benefits outweigh the risks
    - - This is how risky a person thinks something is
      - It is not the same as actual risk and the perceived risk can vary from person to person
- - - - If they are moving slow enough, they will be absorbed by another nucleus and cause a chain reaction of fission to occur
    - - A neutron is added to create the nucleus unstable so radioactive so it emits radiation to become stable again
    - - This makes steam to turn turbines and generators
    - - This is done using control rods
        
        They are lowered and raised inside a nuclear reactor to absorb neutrons and so slow down the chain reaction and control the amount of energy released
      - Uncontrolled chain reactions quickly lead to lots of energy being released as an explosion - this is how nuclear weapons work
    - - The no. of protons/neutrons must be balanced on both sides (conservation of mass)
  - - - This is because some of the mass is converted into energy and then released as radiation
    - - The temperature and pressure needed are so high that fusion reactors are really hard and expensive to build