Atomic structure Flashcards
Why does a nucleus give out radiation?
Some atomic nuclei are unstable, so the nucleus gives out radiation
as it changes to become more stable. This is a random process
called radioactive decay.
What is meant by count rate?
Count-rate is the number of decays recorded each second by a
detector (e.g., Geiger-Muller tube).
What is activity and how is it measured?
Activity is the rate at which a source of unstable nuclei decays.
Activity is measured in becquerel (Bq).
What are the four different types of nuclear radiation?
Alpha (α)
Beta (β)
Gamma (y)
Neutron (n)
What do all the types of nuclear radiation consist?
• an alpha particle (α) – this consists of two neutrons and two
protons, it is the same as a helium nucleus
• a beta particle (β) – a high-speed electron ejected from the
nucleus as a neutron turns into a proton
• a gamma ray (γ) – electromagnetic radiation from the nucleus
• a neutron (n).
what object will absorb alpha from passing on?
Alpha is absorbed by a few centimetres of air or a thin sheet of paper.
What object will absorb Beta from passing on?
Beta passes through air and paper but is absorbed by a few millimetres of aluminium.
What object will absorb gamma from passing on?
Gamma is very penetrating and needs many centimetres of lead or many metres of concrete to absorb most of it.
Which type of radiation is the least ionising and which is the most ionising?
Most ionising is Alpha, and the least ionising is Gamma.
What is the half life?
The half-life of a radioactive isotope is the time it takes for the
number of nuclei of the isotope in a sample to halve, or the time it
takes for the count rate (or activity) from a sample containing the
isotope to fall to half its initial level.
What is radioactive contamination?
Radioactive contamination is the unwanted presence of materials
containing radioactive atoms on other materials.
What is the hazard from contamination?
The hazard from contamination is due to the decay of the contaminating atoms. The
type of radiation emitted affects the level of hazard.
What is irradiation?
Irradiation is the process of exposing an object to nuclear radiation and the irradiated object does not become radioactive.
What are nuclear equations used for?
Nuclear equations are used to represent radioactive decay.
What happens with an alpha particle decay in the radioactive decay?
The mass number of the element is reduced by 4.
The atomic number is reduced by 2.
