Radioactivity 7 Flashcards
what is in the nucleus
protons and neutrons- which make up most of the mass of the atoms
what is the atomic number
no. protons
what is mass number aka nucleon number
protons and neutrons
what gives the atom its overall size?
the electrons
are atoms positively, negatively, or neutrally charged?
neutrally
what is an isotope
an atom with a different number of neutrons, but the same number of protons and electrons e.g., Carbon-14 and Carbon-16
what does an isotope tend to be?
they tend to be radioactive, meaning the nucleus is unstable, so it decays (breaks down), and emits radiation. e.g., Carbon-14 is an unstable isotope of carbon
what is radioactive decay?
a random process
what is the mass and charge (by comparison to a proton) of a proton, neutron, and electron?
proton- mass=1, charge=1
neutron- mass=1 charge=0
electron- mass=1/1840 charge=-1
what is an ion? how are they made? what is the process called?
when an electron is either added or removed. they are made in pairs because an electron that is removed from one atom attracts itself to another atom so an anion and cation pair is formed. this is called ionisation.
what determines what element and atom is?
no. protons
what is a becquerel?
1 Bq= an emission of 1 particle/second
what is radioactive decay?
a random process
what happens in unstable atoms (in the nuclei)? is it affected by anything?
the nuclei break down at random. It is completely random and unaffected by physical conditions like temp or by any sort of chemical bonding etc.
what type of radiation takes place if a nucleus does decay
alpha, beta, gamma, or neutrons
what usually happens during radioactive decay?
the nucleus often changes into a new element
what is background radiation? where does it come from?
the idea that there is low-level background nuclear radiation all around us all the time. It comes from: substances on earth e.g., air food, building materials, soil, rocks, it comes from radiation form space (cosmic rays) - mostly from the sun, living things, radiation due to human activity e.g., fallout from nuclear explosions, or nuclear waste (not a big proportion of total radiation)
what are alpha, beta, gamma an example of?
ionising radiation
what does nuclear radiation cause?
ionisation by bashing into atoms and knocking electrons off them. Atoms with no overall charge are turned into ions
how can you detect ionising radiation?
using a Geiger muller detector or photographic film
finish the sentence: the further the radiation can penetrate before hitting an atom and getting stopped….
the less damage it will do along the way and so the less ionising it is
what are alpha particles? describe them
are nuclei of helium atoms. they are made up of 2 protons and neutrons.
they are big, heavy, slow-moving, therefore they don’t penetrate fast but are stopped quickly. They are strongly ionising (meaning they bash into a lot of atoms and knock electrons off)
so, when an alpha particle is emitted from a nucleus, the nucleus changes into another nucleus with a mass no. 4 less and atomic number of 2 less. ONLY HEAVY ELEMENTS CAN EMIT ALPHA PARTICLES. this is called alpha decay
what are beta particles? describe them.
they are electrons. it is made and ejected from a nucleus when a neutron turns into a proton and an electron. it doesn’t alter mass number but it increases the atomic number of the nucleus by one (because of the proton). this is called beta decay.
they move fast and are quite small. they penetrate moderately and are moderately ionising. ``because they are charged (negatively), beta particles are deflected by electric and magnetic fields
what are beta particles?
electrons
what are gamma rays?
very short wavelength EM waves
what is special about gamma rays
they have no mass or charge, they are just energy
describe gamma rays
short-wavelength EM waves, opposite of alpha particles-just energy, can penetrate a long way into materials without being stopped, they are weakly ionising because they tend to pass through rather than collide with atoms (but eventually they do hit something and cause damage), they have no charge so they are not deflected by electric or magnetic fields, they always happen after beta or alpha decay (you NEVER get just gamma rays emitted), gamma rays have no effect on the atomic mass or mass numbers of the isotope (- if a nucleus has excess energy it loses this energy by hitting a gamma ray)
what are alpha particles blocked by?
paper, skin, a few cm of air
what are beta particles blocked by?
thin metal
what are gamma rays blocked by?
thick lead or very thick concreate
how can you investigate the penetration of radiation?
you can detect ti with a geiger-muller detector. it gives a count rate of the no. radioactive particles reaching it per second. Set up the detector, material and radioactive source and then remove the source to measure the background count over a period of time. divide the cound by the period measured and then find the mean. subtract his from your final results.
Put the source back in and measure the cound with no material present, then inset different materials (do each step several times to get a mean)
if the count ratw stays around the same when a material is inserted, it can penetrate it however if it drops to zero after BR is subtracted then the radiation is completely absorbed. repeat this with different sourcess
how to make sure you are keeping radioactive sources safe?
they should be kept in a lead-lined box when not in use, they should only be picked up using long-handled tongs or forceps. you should take care not to point them at anyone and keep a safe distance from them
can neutrons be emitted from unstable nuclei?
yes
what is half life?
the time taken for half of the radioactive atoms now present to decay
what does a short half life mean?
the radioactive activity falls quickly, because lots of nuclei decay quickly. a long half life on the other hand means the activity falls more slowly because most of the nuclei don’t decay for a long time
how can you measure half life?
using a geiger muller (G-M) detector. you can plot it on a graph and Bq is on the axis whereas time is on the x-axis.
Half-life is found by finding the time interval corresponding to the halving of the activity
MAKE SURE TO SUBTRACT BACKGROUND COUNT FORM ALL READINGS
what materials can be used to detect radioactivity? relate this to the penetrating power of each type of radiation.
aluminium (few mm thick-beta), thick piece of lead (gamma), sheet of paper (alpha)
what can ionising radiation do?
damage cells and tissues
what makes beta and gamma more dangerous than alpha? where?
they can penetrate the skin and soft tissues to reach the delicate organs inside the body, making it more hazardous than alpha OUTSIDE THE BODY.
HOWEVER, if they get inside their radiation mostly passes straight out without doing much damage
Can alpha particles penetrate the skin? where can they cause damage?
alpha particles can’t penetrate the skin but it is very dangerous if it gets inside the body because alpha sources do all their damage in a very localised area.
this si also because thye are strongly ionising.
this can happen if you breath in radioactive gas
what happens when radiation enters your body? lower vs higher doses?
it will collide with molecules in your cells. these collisions cause ionisation which can damage or destroy molecules. the extent of harmful effects depends on exposure, energy, and penetration.
lower doses - can cause minor damage without killing cell, can cause mutations in cell which then divide uncontrollably causing cancer
higher doses- tend to kill cells completely causing radiation sickness if a large part of your body is affected at the same time
what can exposure to radiation cause?
irradiation, meaning they are exposed to it (e.g., humans are always being irradiated by background radiation sources). THIS DOES NOT MAKE IT RADIOACTIVE
what can reduce risk of irradiation?
keeping sources in lead-lined boxes in a different room or behind a barrier
what is contamination
when unwanted radioactive atoms get onto/into an object, the object is said to be contaminated e.g., touching a radioactive source without gloves
can contaminating atoms cause harm or not? what does this means for people who work around radiation?
they can as the contaminating atoms might decay, releasing radiation, which can cause you harm. this is especially dangerous because they could get inside your body.
this means gloves and tongs should be used when handling sources to avoid particles getting onto your skin/under nails.
some industrial workers wear protective suits and masks to stop them from breathing in particles
is radioactive waste easy to dispose of safely? how can you dispose of it?
most is not easy. you can dispose of radioactive waste from nuclear power stations and hospitals (because it is low-level) by burying it in landfill sites
high-level waste is dangerous and can take 10,000+++ years to decay. it is often sealed in glass blocks which are then sealed in metal canisters which could then be bruied deep in the ground but it is difficult finding suitable places to bury it.
why can it be difficult to find a place to bury high level waste?
it has to be in a place that is geographically stable (i.e. no earthquakes) because big movements in the rock could disturb the canister and allow radioactive material to leak out, If it gets into groundwater it could contaminate soil, plants, rivers etc., and get into drinking water
what is the symbol for an hour? minute, second, centimetre, becquerel?
h, min, s, cm, Bq
what can radioactive tracers do?
help doctors examine the insides of our bodies .g., Iodine-123 can be used to see if our thyroid glands (in the throat) are working properly. this is because thyroid glands absorb iodine so a dose of radioactive iodine (the tracer) is given to a patient. the doctor can then detect radioactivity of the patient’s throat.
what can cobalt-60 be used for?
- emits very energetic gamma rays
- kills bacteria to sterilise equipment
- this is done by sealing equipment into a plastic bag and then exposed to radiation
- IT CAN ALSO BE USED FOR RADIOGRAPHERS FOR CANCER treatment to kill cancer cells by directing a strong beam of radiation onto the cancerous tissue. this radiotherapy treatment can have side effects
how can radioactive tracers be used in industry?
to detect metal leaks in underground pipes. you feed the tracer into a pipe and the a G-M tube can be used to detect levels of radiation
what can indirect damage to radiation do to the body?
radiation produces ions which can make strong acids in our bodies. these acids can destroy our cells or cause mutations in our genes
how can we measure doses of radiation?
in sieverts, Sv
practice writing out some equations with alpha gamma beta
is half life different for different radioactive isotopes?
yes
what are the main dangers of ionising radiation?
- can cause mutations in living organisms
can damage cells and tissue - problems can arise from the disposal of radioactive waste
