unit seven: radioactivity and emissions Flashcards
symbol for alpha radiation
a
symbol for beta radiation
β- or β+
symbol for gamma radiation
g
symbol for neutron radiation
n
what is alpha radiation made from
a helium nucleus: 2 protons and 2 neutrons
what is beta radiation from
a high speed electron or beta particle
what is gamma radiation made from
a high energy wave
properties of the gamma wave radiation
high frequency
short wavelength
what does alpha radiation do to the atomic number of the parent atom
decrease by 2 (2 protons and 2 neutrons)
what does beta radiation do to the atomic number of the parent atom
decrease by 1 (1 electron)
what does gamma radiation do to the atomic number of the parent atom
nothing
what does neutron radiation do to the atomic number of the parent atom
nothing
what is neutron radiation made from
an emitted neutron
what does alpha radiation do to the mass number of the parent atom
decrease by 4 (2 protons and 2 neutrons)
what does beta radiation do to the mass number of the parent atom
nothing
what does gamma radiation do to the mass number of the parent atom
nothing
what does neutron radiation do to the mass number of the parent atom
decrease by 1 (1 neutron)
what happens when you fire an alpha particle
the atoms interact with other atoms along their path causing ions to form
what happens when you fire a beta particle
the atoms interact with other atoms along their path causing ions to form, but less frequently then alpha as beta particles are smaller than alpha particles and carry less charge
what charge does a beta particle have
-1
order alpha beta gamma in order of ionising power
alpha (strongest)
beta
gamma (weakest)
what is alpha stopped by
paper
what is beta stopped by
thin aluminium
what is gamma stopped by
thick lead sheet
what is the only type of radiation that can cause other atoms to become radioactive
neutron
what happens during alpha decay
loss of 2 protons and 2 neutrons
= mass number decreases by 4
= atomic number decreases by 2
what happens during beta decay
neutron breaks down to give a proton and an (emitted) electron
= mass number stays the same
= atomic number increases by 1
what happens during gamma decay
a gamma ray is emitted (not charged)
gamma ray energy is 1 x 10 to the minus 12 joules.
what happens during neutron decay
high speed neutron emitted
= atomic number stays the same
= mass number decreases by 1
what is half-life
the time taken for half the original number of unstable nuclei to decay. The half-life of a particular radioactive isotope does not change.
what is rate of decay measured in
becquerels, Bq
what is one Bequerel
one decay per second
explain natural background radiation from earth
when earth was formed it produced many radioactive isotopes. uranium was produced, and it also decays very slowly producing gases as it does so. these gases come out of rocks, and this means radiation from the big bang is still present, being released through rocks in the earth.
explain natural background radiation from space
supernovae produce cosmic rays that coninuously hit the earth. lower energy cosmic rays are given out by the sun. the earth can only protect us from some of these rays
explain radiation in living things
the atoms in our bodies were made from violent reactions. as some of these atoms are raditoactive, and we constantly breathe in tiny amounts of radioactive carbon-14, and it behaves chemically just like the stable isotope carbon-12, we continuously renew the amounts of carbon in our bodies.
explain artificial radiation (examples)
nuclear power stations
nuclear weapons
radioactive tracers
how is radiation used in medicine
radioactive tracers
iodine-123 can be absorbed by thyroid gland allowing clear images to be taken
techtium-99 medical imaging
can be used to kill cancerous cells
industrial applications of radioactivity
gamma rays used to examine contents of luggage
to gauge how much material there is in a storage container
to gauge thickness of sheets
to check flow of liquids
carbon-dating
what is contamination
Contamination - radioactive material has been transferred into a different substance, it will remain radioactive until the radioactive substance has decayed to a safe level.
what is irradation
a material has been dosed with radiation to kill germs etc, when the radiation is stopped, there is no radioactivity in the sample.
dangers of ionising to living things
damages dna within cells
exposed material will give out light when warmed
how is radioactive waste handled/safety precautions
kept in lead lined containers
large samples handled remotely
sealed in containers capable of handling it for massive amounts of time
which element is the fuel rods of reactors
uranium
which isotope is used for nuclear fission
uranium-235
how many uranium pellets are in a whole reactor
over 2 000 000
what substance is used to slow down neutrons in a nuclear reactor
water
what happens when the neutron hits the nucleus of the uranium atom
It causes the nucleus to split in two. (the fission) and releases its own neutrons, hitting other nuclei and causing more fisson.
what particles are released when fission happens
neutrons
what is a chain reaction in the context of nuclear fission
neutrons emitted from the initial collision hit other nuclei causing more neutrons to be emitted
how many fissions happen a second in the reactor
5 million million
what does the hot water from the reactor do after it leaves the reactor
The water hits more than 300 degrees celsius and the heated high pressure water travels out through pipes out of the reactor vessel at 35 mph through
what is the output of the power station
1000 MV
what isotopes of hydrogen collide at high speed during fusion
deutrieum and tritium
what forms as a result of the collision between deutrieum and tritium
a helium nucleus
a neutron
large amount of energy
what is the fusion process an energy source of
the sun and all stars
advantages of fusion
does not produce radioactive waste
uses materials more readily available than the uranium found in conventionalfission reactors
problem with fission
very very high temperatures (100 milion celsius) are needed to make the deuterium and tritium collide with enough energy to overcome the repulsive force between the positive electric charge in the nuclei of each atom
what must the very high temperatures needed for fusion be stored in
a very strong magnetic field or magnetic bottle. the pressure must be very high.
how much smaller is the electron compared to the diameter of the atom
the diameter of the nucleus is about 10,000 times smaller than the diameter of the atom
what symbol is given to atomic number
Z
what symbol is given to atomic mass
A
what determines atomic mass
total number of protons and neutrons
what determines atomic number
number of electrons
what is an isotope
an atom with the same number of protons and different numbers of neutrons
physical differences in isotopes
mass
stability of nucleus
why does stability of isotopes vary
protons are held in place by nuclear force, which stops the protons repelling away from eachother. the neutrons affect the balance, and cause unstability
describe the range of alpha radiation
short ionising radiaiton range.
which is lighter beta or alpha
definitely beta
why does beta have a higher range than alpha
beta particles are smaller and carry less charge so interact with other particlesl ess, so they have a greater range, and can travel long distances.
why do alpha particels have a short range
they interact with atoms along their paths causing ions to form. this means they rapidly give up energythat they had when they were ejected from the unstable nucleus.
describe gamma rays
very short wavelengths. no mass and no charge. weakly ionising
do gamma rays have a large range
yes they are extremely penetrating (as they are weakly ionising and only interact with a few atoms in their path) and can pass through all but the very densest materials.
how must radioactive sources be stored
in lead-lined boxes in a metal cupoboard with radiation warning label
how did henri bequel test if uranium emitted -rays after being exposed to sunlight and what were the results
placed some wrapped, unused photographic plates in a drawer with some samples of uranium ore on top of them. he fpund a stron image of th eore on the plates when he developed them. he had discovered radioactivity
what does the unit the Becquerel measure
the measure of how many unstable nuclei are disintegrating per second
what does one becquerel mean
a rate of one disintegration per second.
what is a kBq
a rate of 1000 disintegrations per second
what is a MBq
a rate of 1 000 000 disintegrations per second
what is a Geiger-Muller tube
a glass tube with an electrically conducting surface on the inside. the tube has a thin window made of mica, and the tube contains a special mixture of gasesat a very low pressure. inside, there is an electrode. this electrode is connected via a high value resistor to a high voltage supply, typically 300-500 V.`
what is mica
a naturally ocuring mineal that can be spit into thin sheets
how does a GM tube work
when ionising radiation enters the tube it causes the low pressure gas inside to form ions. these allow a small amount of current to flow from the electrode to the conducting layer. it is usuallly linked up to a counting circuit. this keeps a count of how many ionising particles or how much y radiation have entered the GM tube.
sources of natural background radiation from the earth
rocks in the earths’ crusts (some of which are still producing radiation) which can be released through radioactive rocks (if gases),
forms of uranium that are decaying very slowly
radon and thoron
how is the natural background radiation from space
violent nuclear reactions in stars and exploding stars called supernovae produce cosmic rays (very energetic particles) that continuously hit the earth. lower energy cosmic rays are given out by the sun.
radiation in living things
the atoms that make up our bodies were formed in the violent reactions that take place in supernovae billions of years ago. we also breathe in tiny amounts of carbon-14
artifical radiation
generating electricity in nuclear power stations leaks radioactive material into the environment.
testing nuclear weapons
radioactive tracers are used in industry and medicine
is radioactive decay random
yes you cannot predict it with certainty
what is halflife def
the average time taken for half the original mass of the sample to decay. if the amount of radioactive matter has halved then the activity of the decay haves.
does the half life vary
yes it is different for every isotope
how do you measure half life
use a GM tube linked to a rate meter. subtract background radiation. then measure the rate of decay of the sample at regular time intervals. the rate of decay is shown by the count rate on the rate meter.
how to record measuring half life
overall title: average background radiation measured over x minutes
then columns of:
time, t/min count rate/Bq corrected count rate C/Bq
the rate of decay is proportional to…
the amount of radioactive isotope present
which isotopes are suited to medical use and why
isotopes with short half lives because the activity of a source will become very small as the isotope decays quickly.
