Radioactivity Flashcards
(31 cards)
what is an isotope ?
atoms with the same number of protons but different number of neutrons
explain what an unstable / stable isotope is
each element only has one or two stable isotopes with a stable nucleus, the others tend to be radioactive due to the unstable nucleus so decays and emits radiation
what is radioactive decay ?
a random and spontaneous process where the nuclei decays, often becoming a new element and spitting out radiation (alpha/beta/gamma)
where does background radiation come from?
substances on earth
space
living things
human activity (explosions)
what is ionisation ?
electrons being knocked off by nuclear radiation, turning the atoms into ions
the further the radiation penetrates before hitting the atom and getting stopped, the less damage/ionising it will do
how can we detect ionising radiation ?
photographic film or Geiger-Muller detector
Describe alpha particles (He²⁺)
Helium nuclei made up of 2 protons and 2 neutrons
(big, heavy, slow moving)
so don’t penetrate far (skin or paper)
size makes them very ionising
electrically charged means they are deflected by electric and magnetic fields
POSITIVE CHARGE
Describe beta particles (e-)
an electron which has been emitted from nucleus of an atom when a neutron turns into a proton and an electron
move fast and are quite small
moderately penetrating (aluminium) and ionising
deflected by electric and magnetic fields
NEGATIVE CHARGE
Describe gamma rays (γ)
have no mass as they are just energy (EM waves)
can penetrate far (thick lead)
weak ionising as they pass through instead of colliding with atoms, but do eventually and do damage
gamma comes after beta and alpha decay
if nucleus has excess energy, it is lost by emitting gamma
what blocks alpha
paper, skin or a few centimetres of air
what blocks beta
thin metal (aluminium)
what blocks gamma
thick lead or very thick concrete
state the 3 points of alpha scattering
the faster a alpha particle goes, the less likely it will be deflected by a nucleus the more (+ve) charged a nucleus is (high atomic number) the more alpha will be deflected the closer an alpha particle pass to the nucleus, the more it will be deflected
define half life
time taken for half of the radioactive atoms now present to decay
what is a short half-life ?
activity falls quickly because lots of nuclei decay quickly
what is a long half-life ?
activity falls slowly because most of the nuclei don’t decay for a long time
how do medical tracers work?
source of beta/gamma (short-life) radiation is put into patient
radiation penetrates skin so can be detected
radiographer uses detector to monitor progress
computer converts reading into screen display, showing where radiation is coming from
used to check whether organs are fine
How to use gamma in pipes?
squirt gamma source (short-life) into pipe, let it flow and go along with detector
if there’s a crack, detector will show extra high radioactivity
when can alpha particles be dangerous ?
when they get inside your body as they are very ionising and won’t be able to get out
how does radiation damage the body?
collides with molecules, causing ionisation, which causes mutations which then divide uncontrollably or even kills cells, causing radiation sickness
what is radiotherapy ?
using high does of gamma rays carefully zapped onto the tumour cells to kill them
describe the disposal of radioactive waste
very difficult as high-level waste can take tens of thousands of years to go so is often sealed in glass blocks, which are sealed in metal canisters and buried deep in the ground
the site must be geologically stable (no earthquakes) so it doesn’t leak and get into ground water
how to keep safe with radioactive materials?
never allow skin contact so use tongs at arms length
keep source pointed away from body and don’t look directly at it
store in sealed lead box
what do regular radioactive workers do?
medical workers wear lead aprons behind lead screens
nuclear workers wear full protective suits
they can also use remote controlled robot arms
