4.2 ATOMS AND NUCLEAR RADIATION Flashcards
Why do unstable nuclei give out
radiation?
● Unstable nuclei undergo decay to
become more stable
● As they release radiation their stability
increases
What is the name of the process in which
an unstable nucleus gives out radiation
to become more stable?
Radioactive decay.
Define the activity of an unstable
nucleus.
Activity is the rate of decay of a source of
unstable nuclei.
What is the unit of radioactive activity?
Becquerel (Bq)
What is count-rate?
The number of radioactive decays per
second for a radioactive source
Give an example of a detector that may
be used to measure count-rate.
Geiger-Muller tube
State four types of nuclear radiation.
- Alpha particles
- Beta particles
- Gamma rays
- Neutrons
What are the constituents of an alpha
particle?
● Two protons and two neutrons
● It is the same as a helium nucleus
What is the range of an alpha particle
through air?
A few centimetres (normally in the range
of 2-10cm).
What will stop beta radiation from
passing through a point?
● A thin sheet of aluminium
● Several metres of air
What will stop gamma radiation from
passing through a point?
● Several centimetres of lead
● A few metres of concrete
Which type of radiation is most ionising?
Alpha radiation.
Which type of radiation is least ionising?
Gamma radiation.
State any changes to mass or charge
that occur due to the emission of a
gamma ray.
Both mass and charge remain
unchanged.
Describe the nature of radioactive decay.
● Random ● Which nuclei decays and when is determined only by chance ● It is impossible to predict which nuclei will decay and when
Define the half-life of a radioactive
isotope.
● The time it takes for the number of unstable nuclei in a substance to halve ● The time it takes for the count rate from a sample to fall to half its initial level
What is radioactive contamination?
The presence of unwanted radioactive
nuclei on other materials.
What is irradiation?
● The process of exposing a material to
nuclear radiation
● The material does not become
radioactive
Why is it important for the results of
studies on the effects of radiation to be
published and shared with other
scientists?
● To allow the findings to be
independently checked
● This is known as peer review
