SP6 - Radioactivity ✓ Flashcards Preview

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Flashcards in SP6 - Radioactivity ✓ Deck (56)
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SP6a - What did the plum pudding model look like?

Made of positively charged mass with negatively charged electrons scattered throughout.


SP6a - What was the experiment that Erenest Rutherford conducted and what did he do?

  • The gold foil experiment.
  • He fired alpha particles through various substances e.g. thin gold foil.
  • Firing alpha particles from a source and having a detector behind whatever substance he used so that he could find out if the particles pass through.


SP6a - What were the results drawn of the gold foil experiment and what conclusions were drawn from this?

  • Most particles passed straight through
  • Some were deflected slightly
  • Others were bounced back
  • This means that most of an atom is empty space.
  • Aditionally, atoms have a concentrated area of positive charge.
  • This is why some were reflected back.


SP6a - What is the radius of a nucleus and the radius of an atom?

  • N: 1x10-15
  • A: 1x10-10

(Atom is 10,000 times bigger)


SP6b - What are the charges, locations and relative masses of protons neutrons and electrons?


  • Inside nucleus
  • +1 charge
  • mass of 1


  • Inside nucleus,
  • no charge
  • mass of 1


  • Orbiting nucleus
  • -1 charge
  • mass of 1/1835 (negligible)


SP6b - What does the atomic number of an atom represent?

  • The number of protons in the nucleus.
  • Different elements have different proton numbers


SP6b - What does the mass number of an atom represent?

  • The mass of the atom.
  • Protons plus neutrons.


SP6b - What is an isotope?

Two atoms of the same element with different masses (Same atomic number but different mass numbers)


SP6c - What can happen if an atom gains enough energy and what does this create?

  • An electron can move to a higher orbit.
  • When it returns back to its orbit it emits energy in the form of visible light.
  • The wavelength (and therefore colour) depends on the change in orbit.


SP6c - What do we use to see the light produced by an atom?

  • An emission spectrum.
  • A black line spectrum with coloured lines along it displaying which wavelengths were emitted.


SP6c - How will the emission spectrum of an element relate to its absorption spectrum and what does this tell us?

  • The coloured areas on the emission spectrum will be blacked out on the absorption spectrum and vice versa.
  • This means that the wavelengths that are emitted are also the wavelengths that are absorbed.


SP6c - If an atom gains more energy than needed to just move an electron to another orbit, what can happen and what is this called?

  • The atom can loose an electron.
  • This is called ionisation as the atom has become an ion


SP6c - What is an ion?

An atom that is charged due to a gain or loss of electrons.


SP6c - What do we call radiation that causes an atom to loose an electron?

Ionising radiation


SP6d - What is background radiation?

Radiation that is constantly all around us at a safe level.


SP6d - What are the six main sources of background radiation

  • Medical
  • Ground and buildings
  • Food and drink
  • Radon gas
  • Cosmic rays
  • Nucelar


SP6d - Which source of backgrond radiation accounts for most of it and approximately how much is it?

Radon gas just under 50%


SP6d - What are ways of measuring radioactivity?

  • With a Geiger
  • Mueller tube / counter Meausres the count rate
  • Photographic film (badges called dosimeters) Gets darker / changes colour as its exposed to more radioactivity


SP6d - Before measuring the radioactivity of a source what must be done?

Measure the background radiation so you can take this away from the radiation that you measure or else you value will be the source's radiation + the background radiation.


SP6e - What is an alpha particle?

A helium nucleus consisting of 2 protons and 2 neutrons


SP6e - What is a beta minus particle?

An electron


SP6e - What is a beta plus particle?

A position (A positive electron)


SP6e - What don't gamma rays have that other radiation does.

Since it is an EM wave and not a particle, it doesn't have a charge.


SP6e - Rank and explain the types of radiation in terms of ionisation.

  • Alpha (Most)
  • Beta (+/-)
  • Gamma (Least)

Since alpha particles are emitted at high speeds thay carry most energy and are best at ionistation.

This is the opposite for Gamma.


SP6e - Rank the types of radiation in terms of penetration / range.

  • Gamma (Most)
  • Beta (+/-)
  • Alpha (Least)


SP6e - What does it take to stop each type of radiation?

  • Alpha: paper/skin/few cm of air
  • Beta: few m of air/3mm of alluminium
  • Gamma: few Km of air/ few cm of lead/ several m of concrete


SP6f - What occurs in alpha decay?

An unstable nucleus looses 2 protons and 2 neutrons (an alpha particle) causing its mass number to decrease by 4 and its atomic number to decrease by 2.


SP6f - What occurs in beta minus decay?

A neutron decays into a proton and a high energy electron.


SP6f - What occurs in beta plus decay?

A proton decays into a neutron and a high energy positron.


SP6f - What occurs in gamma decay?

An unstable nucleus emits a gamma ray becoming more stable.