7b P1 radioactivity LM fission and fusion Flashcards
what happens when isotopes are unstable?
undergo radioactive decay, so they emit electrons
what are alpha particles made up off?
2 protons and 2 neutrons, no electrons same as nucleus of Helium
how do we represent alpha particles?
He or helium symbol
what is the overall charge for alpha particles?
2+ because they have no electrons, and neutrons have a neutral charge
how penetrating are alpha particles?
can’t penetrate far into other materials
- can only travel a few cm in air
- absorbed by a single sheet of paper
how ionising are alpha particles?
very
- because of large size and strong charge
what does strongly ionising mean?
easily knock electrons off of any atoms they collide with
what are beta particles?
just an electron, charge of -1 and no mass
how are beta particles made?
- one of the atoms neutrons decays into a proton and an electron
- proton stays in the nucleus, electron emitted at high speed
how ionising are beta particles?
moderately
how penetrating are beta particles?
penetrate moderately far
- several meters of air and 5mm of aluminium to stop them
what are gamma rays?
waves of electromagnetic radiation
when are gamma rays emitted?
often emitted after alpha or beta radiation, a way of getting rid of a bit of extra energy
how penetrating are gamma rays?
penetrate really far
- long distances
- thick sheets of lead
- meters of concrete to stop them
how ionising are gamma rays?
weakly because they have no mass or charge
what is the last type of radiation?
emission of a neutron
what happens to an atom that has too many neutrons?
wants to become stable so it throws out a neutron to increase stability
what happens in an alpha decay ?
when an unstable nucleus undergos alpha decay, it emits an alpha particle
- have to subtract 4 from mass number
- subtract 2 from atomic number
the nucleus will change and then it will most likely become something else
what happens in beta decay?
neutron turns into a proton and emits a beta particle
- gains a proton so atomic number changes (changes element as well)
- mass number stays the same
- e (beta particle) has an -1 and a 0
why does the mass number in beta decay stay the same?
gained a proton, but it also lost a neutron
what happens in gamma radiation and the equation?
if an element underwent gamma radiation it stays the same plus gamma radiation (weird v thing)
what is the equation for neutron emission?
subtract one from the mass number of the element , and a neutron on the end
what is a half life?
- the time taken for the number of radioactive nuclei in a sample to halve
- the take time for the number of decays or activity to halve
both are correlated
what is the activity in terms of decay?
overall rate of decay of all the isotopes in our sample
what is activity measured in?
becquerels
1Bq = 1 decay per second s
how do you know when a particle will decay?
you don’t, you can’t tell its completely random
as the number of particles decrease…
the overall rate of decay or activity also decreases
the half life of a radioactive source is 40 hrs, there are initially 3,000000 radioactive nuclei in the sample. how many nuclei will remain after 5 days?
- how many half lives?
5days x 24 hrs
= 120 /40h = 3 half lives - halve the no. of nuclei that many times.
so just half the initial number of radioactive nuclei three times because there are three half lives
what is contamination?
when radioactive particles get onto other objects
what is irradiation?
the process by which objects/things are expose to radiation of any type
what are non ionising radiation ways?>
ultraviolet
and microwave
why is contamination harmful?
isn’t but the particle on you is likely to decay and then irradiate the object, its the risk that is the issue
what determines how harmful radiation is?
- what type
- where is the exposure
- the amount
what are the more harmful types of radiation?
ionising, because they can enter living cells and interact with the molecules inside, ionise our DNA, that cause mutations
what is the most harmful type of radiation when the source is outside the body?
beta and gamma because they can penetrate
what is the most harmful type of radiation when the source is on or inside the body?
alpha is the most because it would make it to cells inside the body
what precautions can reduce your risk of being contaminated or irradiated?
gloves
overalls
using tongs
keeping item in lead lined box
what are the uses of radiation in medicine?
radiotherapy medical traces (X-rays etc)
what is radiotherapy?
to destroy particular cells, mainly cancerous cells
what are the two types of radiotherapy?
externally and internally
how does external radiotherapy work?
gamma rays are targeted at the cancer site at lots of different angles
cancer site gets the highest dose
how does internal radiotherapy work?
beta rays
