p7 radioactivity Flashcards
What is the radius of an atom?
1 x 10^-10
This is a typical size for an atom.
What happens when an atom absorbs electromagnetic radiation?
An electron can move from a lower energy level to a higher energy level, moving away from the nucleus.
What occurs when an electron returns to a lower energy level?
The atom emits electromagnetic radiation.
What is radioactive decay?
A random process where unstable nuclei emit nuclear radiation to become more stable.
How is activity defined in the context of radioactive decay?
The rate at which a source of unstable nuclei decay, measured in becquerel (Bq).
What device is used to measure activity?
Geiger-Muller tube.
What types of particles can be emitted by unstable nuclei?
- Alpha particles (α)
- Beta particles (β)
- Gamma particles (γ)
- Neutrons (n)
What is an alpha particle?
Consists of 2 protons joined to 2 neutrons; the same as a helium nucleus.
What happens to the atomic number and mass number during alpha decay?
Atomic number goes down by 2, mass number goes down by 4.
What is a beta particle?
A high speed electron ejected from the nucleus.
What occurs in the nucleus when a beta particle is formed?
A neutron changes into a proton and an electron.
What happens to the atomic number during beta decay?
Atomic number goes up by 1, mass number remains unchanged.
What type of radiation is a gamma particle?
A type of electromagnetic radiation from the nucleus.
What happens to the atomic and mass numbers when a gamma particle is emitted?
Both atomic number and mass number stay unchanged.
What is the range in air for alpha particles?
Can travel around 5cm in air before stopping.
What is the penetrating power of alpha particles?
Stopped by a sheet of paper.
Which type of radiation has the highest ionising power?
Alpha particles.
What is half-life?
The time it takes for the number of nuclei of a radioactive isotope in a sample to halve.
How is half-life calculated?
Half-life = initial count rate / 2^n.
What is ionising radiation?
Radiation that can form ions and potentially damage living cells.
What are precautions against ionising radiation?
- Shielding
- Monitoring
- Minimizing time spent in at-risk areas
- Keeping distance from radiation source
What is irradiation?
The process of exposing an object to nuclear radiation without making it radioactive.
What is radioactive contamination?
The unwanted presence of materials containing radioactive atoms on other materials.
How does alpha radiation behave in terms of ionisation?
Strongly ionising but easily stopped by dead cells on skin surface.
What is background radiation?
Radiation that is present around us all the time from natural and man-made sources.
What are the uses of nuclear radiation in medicine?
- Exploring internal organs using medical tracers
- Controlling/destroying unwanted tissues through radiotherapy
What is nuclear fission?
The splitting of a large and unstable nucleus into two smaller nuclei.
What triggers nuclear fission?
An unstable nucleus must first absorb a neutron.
What is nuclear fusion?
The joining of two light nuclei to form a heavier nucleus.
What is released during nuclear fusion?
Energy, which can be converted from the mass of the nuclei.
