P8 Flashcards
Define radioactive decay (3)
process when unstable nuclei “decay”
emit particles or waves to form more stable nuclei
occurs spontaneously + randomly over time
What does a radioactive nucleus emit when it decays (3)
alpha particles
beta particles
gamma rays
Define ionising radiation (2)
stream of radioactive rays/particles
has enough energy to cause other atoms to lose electrons + become cations
Detection of Radioactivity
Geiger-Muller tube
Alpha particle description
positively charged particle
has two protons + two neutrons
Alpha particle penetration (2)
4-10 cm of air
stopped by sheet of paper
Alpha particle electric charge
+2
Alpha particle relative atomic mass
4 atomic units
Alpha particle ionising effect
strongly ionising
Alpha particle effects of magnetic/electric field
weakly deflected in opposite direction to beta
Use of alpha particles (5)
smoke detectors
radiation produces ions in air
ions conduct electric current
smoke absorbs some of alpha particles = reduces ion number + current
sets off alarm
Beta particle description
high energy electron from a nucleus
Beta particle electric charge
-1
Beta particle relative atomic mass
1/1860th of an atomic unit
Beta particle penetration power (2)
1 m of air
stopped by few mm of aluminum
Beta particle ionising effect
weakly ionising
Beta particle effect of magnetic/electic field
strongly deflected in opposite direction to alpha
Gamma ray description
high energy/short-wavelength electromagnetic wave released from an atom
Gamma ray electric charge
electrically neutral
Gamma ray relative atomic mass
no atomic mass
Gamma ray penetrative power (3)
strong penetration at speed of light
no material can completely stop it
strength can be reduced by several cms of lead + metres of concrete
Use of beta particles (2)
medical tracers - checking thickness of material
number of beta particles passing through material is reduced when thickness is increased
Ionising effect of gamma rays
weakly ionising
Magnetic/electric field effect on gamma ray
unaffected
Use of gamma rays
medical industry - sterilisation of medical equiptment + to treat cancer
Define background radiation
radiation from artificial + natural sources
What is meant by radiation being ionising
radiation collides with atom –> removes electrons from atom causing it to become charged
What happens when a nucleus emits an alpha particle
loses 2 protons
nucleon number decreases by 4
What happens when a nucleus emits a beta particle (3)
proton number increases by 1 - 1 neutron changes to proton
gains 1 electron
electron emitted as beta particle
What happens when a nucleus emits a gamma ray (2)
wave carrying energy is emitted
no change to proton or necleon number
Define half-life (2)
time taken for half the radioactive nuclei to decay
measured in becquerels
Define becquerels
1 becquerel = 1 nucleus decay and emits radiation per second
Dangers of alpha particles (2)
dangerous to human tissue - strong ability to ionise other particles
cannot penetrate skin
Dangers of gamma radiation (2)
high penetrating power
cell has repair mechanisms that make ordinary levels of gamma radiation harmless
Safety precautions when handling radiation (4)
forceps when moving radioactive sources
not pointing radioactive sources at living tissue
store radioactive material in lead containers
check surrounding for radiation level above background level
Example of radioactive iodine to treat cancer in thyroid (2)
thyroid cells absorb more iodine than other body parts
iodine absorbed by cancer cells which kills them
Define radiotherapy
radiation fired at cancer cells to kill them
Define radioactive carbon dating (3)
carbon contains small amount of radioactive isotope carbon-14 (half-life of 5700 years)
living material dies = carbon-14 will decay
ratio of carbon-14 nuclei to non-radioactive carbon-12 can calculate age
