What is Radioactivity?
- The characteristic of various materials to emit ionising radiation. The phenomenon of spontaneous disintegration of unstable atomic nuclei to atomic nuclei to form more energetically stable atomic nuclei.
What is ionisation?
The removal of electrons from an atom. The essential characteristic of high energy radiations when interacting with matter.
What are Isotopes?
Atoms of the same species (same number of protons) which vary in neutron number.
Just because you have an isotope doesn’t mean it is radioactive.
The type of decay that a nuclide will typically undergo can be determined by its relationship to the line of stability.
What are Isomers?
Two or more atomic nuclei that have the same atomic number and the same mass number but different energy states.
- The half-life of the isomers will be different.
Half-life is the amount of time taken for radioactivity to reduce to half.
- Cobalt-58 Isomer 1: 71-day half-life (decays by electron capture and positron emission) MORE DANGEROUS
- Cobalt-58m Isomer 2: 9-hour half life (decays by isomeric transition)
What is Isomeric transition?
The decay of a nuclear isomer to a lower-energy nuclear state.
What is meant by Metastable?
Gamma emission with a measurable half life.
What is the Becquerel symbol?
The Becquerel symbol (Bq) is equal to one disintegration or nuclear transformation per second. 1 Bq = 1 s-1.
What is the Curie unit?
A unit of radioactivity, equal to the amount of a radioactive isotope that decays at the rate of 3.7 × 1010 disintegrations per second.
Describe Radioactive decay
Always follows an exponential decrease in activity with time.
What is half life?
- The half-life (T1⁄2) describes the amount of time needed for half of a sample of unstable atoms or particles to undergo decay.
- You can not predict when a particular atom or particle will decay. You only know that, on average, half of a sample will decay during the span of one half-life.
Describe radioactive decay
- All of the decays remove energy from the nucleus.
- Some release just energy.
- Some give energy to a particle which is emitted.
List the types of Radioactive decay
- Alpha
- Beta
- Gamma
Describe Alpha decay
-Alpha decay is the emission of an alpha particle (2 protons and 2 neutrons) from an unstable nucleus.
- 42He2+
- The daughter nuclide has an atomic number 2 less than the parent nuclide and a mass number 4 less than the parent nuclide.
Describe beta decay
- Beta decay is the emission of a beta particle.
- There are two types of beta decay
- Beta minus
- Beta plus
What is a beta minus?
- A b- particle is an electron.
• A neutron is converted to a proton and an electron.
• The electron b- particle is ejected.
n → p + b- + v_
V_ particle with no mass/charge only speed
What is beta plus?
- A b+ particle is an positron.
- A proton is converted to a neutron and a positron.
• The positron b+ particle is ejected.
p → n + b+ + v
What occurs during an electron capture?
- During electron capture, an electron in an atom’s inner shell is drawn into the nucleus where it combines with a proton to form a neutron and a neutrino.
- The neutrino is ejected from the atom’s nucleus.
p + e → n + v
What is gamma emission?
- Gamma decay usually happens after the transmutation of the nucleus; the end product has to re-arrange the occupancy of energy levels in order to arrive at a more stable state.
- In the gamma decay, the emitted photon and recoil nucleus each have a well-defined energy after the decay.
What is internal conversion?
- Internal conversion occurs when a gamma ray, emitted by the nucleus as it goes from the excited state to the ground state, interacts with one of the innermost electrons of the same atom.
- The electron is ejected from the atom
