Radioactivity and Particles - GCSE Flashcards
what is in the centre of every atom?
a nucleus
what does the nucleus of an atom contain?
protons and neutrons
what makes up most of the mass of an atom?
the protons and neutrons inside the nucleus
how is the charge of electrons? and what is their size?
they are negatively charged and really really small
what is the number of proton in a nucleus called?
atomic number or proton number
what does it mean when you say atoms are neutral?
the number of protons = the number of electrons
what is the number of protons and neutrons in the nucleus called?
mass number or nucleon number
what are isotopes?
they are atoms with different numbers of neutrons but same number of protons (so a different mass number)
what can a nuclei of unstable isotopes do?
decay and emit radiation
when and where does nuclear radiation happen?
everywhere and all the time
can you predict when the nuclei of an unstable isotope break down?
no because they break down at random
can you make a decay happen
no
where does background radiation (the one that is everywhere and happening all the time) come from?
(3 points)
- substance here on earth: air, food, building materials, soil, rocks
- from space (cosmic rays) mostly from the Sun
- living things, There is a little bit of radioactive material in all living things due to human activity
what does nuclear radiation cause?
ionisation
how does nuclear radiation cause ionisation?
by bashing into atoms and knocking electrons off them . Atoms with no overall charge are turned into ions (which are charged), creating the term ionisation
what causes there to be less ionisation?
the further the radiation can penetrate before hitting an atom and getting stopped, the less damage it will do along the way and so less ionising it is
what are the 2 things that can detect ionisation?
- a Geiger-Müller detector
- and a photographic film
what are the 3 types of ionsionising radiation?
- alpha
- beta
- gamma
what are alpha particles made up of?
2 protons and 2 neutrons
how does an alpha particle look like? how does it move?
it is big, heavy and slow moving
tip for remembering this -> Alpha reminds me of a leader or king. However, since this particle is a king, it is really fat since it has the money to eat all day. This causes the particle to be heavy (as it fat). And, this particle also is slow moving, since fat people don’t move really fast. No hate.
why do alpha particles don’t penetrate far into materials?
because they are big, heavy and slow moving causing the to be stopped quickly
how ionising are alpha particles and why?
they are strongly ionising meaning they bash into a lot of atoms and knock electrons off them before they slow down, creating lots of ions.
tip for remembering this -> again, remember of the fat king, who is STRONG and powerful and can KNOCK OFF anyone
what type of charge do alpha particles have?
they are electrically charged (positive charge)
what changes the direction of alpha particles? why?
electric and magnetic fields. They can change the direction of alpha particles because alpha particles are electrically charged
what does emitting an alpha particle do to another particle?
it decreases the mass number by 4 and the atomic number by 2
what is a beta particle?
it is a fast moving electron emitted by radioactive decay of substances
what happens when a beta particle is emitted to another particle?
the atomic number increases by 1, however, the mass number stays the same. The number of protons in the nucleus increases by 1
how does a beta particle move and looks like?
they move really quick and are quite small
tips for remembering -> when I think of beta I think of soldiers. Soldiers need to be quick for attack, and small if they want to hide. Also, Scott’s beta in teen wolf was small hehehe
how do beta particles penetrate?
they penetrate moderately before colliding and they are moderately ionising too
what type of charge do beta particles have?
negatively charged
what do electric and magnetic fields do to beta particles?
they deflect (change their direction) beta particles
what are gamma rays?
they are the opposite of alpha rays, they have no mass, they are just energy
tips for remembering -> eles estao GAMANDO pelo dinheiro do alpha (o rei), por que eles nao tem nenhuma MASSA, só ENERGIA para robar o dineiro
how do gamma rays penetrate?
they can penetrate long ways into materials before being stopped
tips for remembering -> they are very sneaky and can get anywhere (just like ocean 11)
why are gamma rays weakly ionising?
because they can pass through rather than having to collide with atoms. Buuuut, eventually they hit something and do damage
what type charge do gamma rays have?
they have no charge so they’re not deflected by electric or magnetic fields
when do gamma rays happen?
after alpha and beta decay, you never get just gamma rays
what effect do gamma rays have on particles?
NO effect on atomic number or mass number
what is 1 important things to keep in mind when balancing nuclear equations?
- the overall charge and mass have to be the same as they were before a nuclear reaction
what happens to particles after alpha, beta, gamma, and neutron emissions?
alpha -> mass number decreases by 4
-> atomic number decreases by 2
beta -> mass number stays the same
-> atomic number increases by 1
gamma -> mass number stays the same
-> atomic number stays the same
neutron -> mass dumber decreases by 1
-> atomic number stays the same
what are alpha particles blocked by?
paper, skin or a few cm of air
what are beta particles blocked by?
thin metal
what are gamma particles blocked by?
thick lead or very thick concrete
how do you investigate the penetrating of radiation?
1) you detect ionising radiation with a Geiger-Müller detector.
2) you set up the equipment by putting setting a Geiger-Müller detector, a radioactive source, and a material in the middle. The Geiger-Müller detector will record a count rate.
3) then, remove the radioactive source so that the detector can measure the background count over a period of time (30 seconds).
4) measure the mean count rate of the radioactive source (minus the mean background count). Now, try with different materials in the middle. Record the count rate for each material 3 times and then find the mean.
5) if the count rate remains the same for all 3 times, the radiation can penetrate the material. If it drops by a large amount, the radiation is being absorbed and blocked. If it drops zero after the background is subtracted, the radiation is being completely absorbed
how does a Geiger-Müller detector detect ionising radiation?
it gives a count rate, the number of radioactive particles reaching it per second
how should you protect yourself from radioactive sources?
radioactive sources should…
- be kept in a lead-lined box when not in use
- should be picked up using forceps
- not be pointed at anyone and kept a safe distance
what is half-life?
the time it takes for a radioactive material to lose half of its radioactivity
over time, what happens to radioactivity?
it decreases
why does radioactive decrease over time?
because each time a decay happens an alpha, beta particle or gamma ray is given out one more radioactive nucleus disappears
what is the fancy definition of half-life?
half-life is the time taken for half of the radioactive atoms now present to decay
what is a short half-life?
it is when the activity falls quickly because lots the nuclei decay quickly
how do you calculate half-life?
example question:
The activity of a radioactive isotope is 640 Bq. Two hours later it has fallen to 40 bq. Find the half-life of the sample
initial count: 640 640 divided by 2 = 320 320 divided by 2 = 160 160 divided by 2 = 80 80 divided by 2 = 40!!
2 (hours) divided by 4 (half-lives) = 30 minutes
answer: It takes 4 half-lives for the activity to fall from 640 to 40 in two hours. Each half-life took 30 minutes
how do you calculate half-life using a sample graph?
you just half to divide the maximum activity the graph got to by two.
which radiations do medical tracers use?
they use gamma or beta radiation
why do medical tracers use gamma or beta radiation?
because these radiations will penetrate through the skin and other body tissues. Alpha won’t
food and equipment can be sterilised using which radiation? and why?
gamma rays. Because it doesn’t involve high temperatures (like boiling water), so fresh fruit and plastic instruments can be sterilised without being damaged
why food can be sterilised by gamma rays?
because with a high dose of gamma rays kill microbes. It does that so that the food won’t go bad as quickly
what other than sterilising is radiation used for?
cancer treatment
how does radiation help treat cancer?
radiotherapy kills cancel cells and stops them from dividing. It involves a high dose of gamma rays, carefully directed to zap the cells in the tumour while minimising the dose to the rest of the body
which ionising radiation the most dangerous for us? damage cells and tissues?
alpha radiation can be very dangerous if it enters the body. When it is outside it is not as dangerous since it cant penetrate the skin. When it enters the
why does ionising radiation damage cells and tissues?
because it collides with molecules in your cells. These collisions cause ionisation, which damages or destroys molecules
what does the harmful effect of ionising radiation depend on?
how much you were exposed to the radiation and its energy and penetration.
what can lower doses of radiation cause?
damage cells without killing them. This can cause mutations in cells which then divide uncontrollably, this is cancer
what can higher doses of radiation cause?
it tends to kill cells completely causing radiation sickness if a large part of you body is affected at the same time
what happens to objects that are near radioactive objects?
they are irritated by it (they are exposed to it)
what is nuclear fission?
the splitting of an atom, which releases energy
what is nuclei fusion?
the opposite of nuclear fission. It is when 2 light nuclei collide at a high speed and join to create a larger, heavier fusion
when does fusion only happen?
it only happens in high temperatures and pressures
