Chapter 25: Radioactivity Flashcards
What is the definition of Radioactivity?
Radioactivity is the process in which an unstable nuclei emits energy (or ionising radiation) in the form of Particles or Waves to form a more stable nuclei.
What is the definition of Alpha Radiation/decay?
Alpha Radiation/decay is the decay of an unstable nuclei through the release of IONISING radiation consisting of Alpha Particles containing 2 Protons and 2 Neutrons and a charge of +2e.
What is the definition of Beta Radiation/decay?
Beta Radiation/decay is the decay of an unstable nuclei through the release of IONISING radiation consisting of a high velocity electron. Beta+ radiation involves converting a proton into a neutron and releases a positron, whilst Beta- decay involves converting a neutron into a proton and releases an electron.
What is the definition of Gamma Radiation?
Gamma decay/radiation is the decay of an unstable nuclei through IONISING radiation consisting of Gamma Waves or High Energy Photons.
What are the effects of Electric Fields on each types of Radiation?
For Radiation in an electric field:
Alpha Radiation will be WEAKLY deflected in a electric field and will deflect towards the negative plate/node.
Beta Radiation will be STRONGLY deflected due to having a much lower mass than Alpha Particles and will deflect towards the positive node.
Gamma Radiation will have NO deflection due to not consisting of particles and no overall charge.
What materials can stop each radiation?
For each radiation, the materials required to stop them are:
Alpha: A thin sheet of Paper.
Beta: Few Centimetres of Aluminium.
Gamma: Several Metres of Lead.
What is the definition of ionising radiation?
Ionising Radiation means that the radiation can ionise atoms by REMOVING electrons from their outer shells to leave a positive ion.
What are the rules for decay equations?
In a decay equation, the sum of numbers on both sides of the equation must add up and are equal.
What is the definition of Half Life?
Half Life is defined as the time taken for half of the radioactive nuclei within a radioactive isotope sample to decay.
What are the properties of radiation?
Radiation is random because we cannot predict when a particular nucleus in a sample will decay, and all nucleus within a sample has an equal chance of decaying per unit time.
Radiation is also spontaneous since the decay of a nucleus is not affected by the other nuclei in a sample and is not affected by external factors. eg: Pressure.
What is the shape of the curve on a Nuclei Number - Time Graph?
The curve on a Nuclei Number - Time Graph will be an exponential decay.
What is the definition of Activity, and how is it calculated?
Activity is defined as the rate at which nuclei within a sample of radioactive substance will decay per unit time, measured in Becquerels.
What is the definition of Count Rate?
Count Rate is defined as the number of decays per second which are detected by the GM Tube. This will usually be smaller than the actual activity since radiation is emitted in all directions and count rate only detects radiation in one specific direction.
What is the definition of the Decay Constant (λ)?
The Decay Constant is defined as the probability in which a nucleus within a radioactive sample will decay per unit time.
What is the equation that links Activity, Decay Constant and Number of undecayed nuclei?
The equation that links Activity, Decay Constant and Number of undecayed nuclei is:
A = λN, Activity = Decay Constant x No. of Undecayed nuclei
What is the exponential equation that links Half Life and decay constant?
The exponential equation that links Half Life and the Decay Constant is:
e^λt(1/2) = 2
Note: Use Natural Log to find the Decay Constant or time.
What is the exponential equation that links Half Life, Decay Constant and Initial Number of Atoms?
The Equation that links Half Life, the Decay Constant and Initial Number of Atoms is:
N₀ / 2 = N₀e^-λt(1/2)
