p6.1 - yr9 bits Flashcards
what happens if a proton number changes of an element?
the element changes
what is a radioactive substance?
one that contains unstable nuclei that become stable by emitting nuclear radiation
what is an alpha particle made of?
2 protons,2 neutrons (ie. a helium NUCLEUS)
what is an alpha particle stopped by?
paper/skin
compare ionising properties of alpha, beta, gamma
alpha - high ionising
beta - moderately ionising
gamma - low ionising
what is beta radiation stopped by?
thin aluminium
what is gamma radiation stopped by?
thick lead/concrete
speed of alpha beta gamma radiation?
alpha - slow
beta - fast
gamma - speed of light (EM wave)
differences between gamma radiation and alpha and beat
gamma is a wave
alpha and beta are particles
range of alpha beta gamma radiation?
alpha - few cm in air
beta - 1m in air
gamma - unlimited range in air
what is a beta particle?
a fast moving electron
how does ionising living cells affect them?
kills/damages them
what is the most dangerous kind of radiation inside the body?
alpha (more heavily ionising) than beta/gamma
- many ions created inside body
what is ionisation?
process of turning a neutral atom/molecule into an ion
why is nuclear radiation so dangerous to the human body?
- nuclear radiation is highly ionising
- if ions are created near the body, they will react with the cells of the body
- which are them damaged
- as the cells are ionised, they become highly reactive and continue to replicate
- giving rise to a tumour
what kind of radiation is most and least dangerous outside the body?
most - gamma (can penetrate skin)
- although lower chance of ionisation
- ions created damage cells of organs
least - alpha (can’t penetrate skin)
- most skin cancer = cut off
what kind of radiation is the least dangerous inside the body?
gamma - can penetrate body and leave it
- ions created are outside body, not damage cells
how are penetrating power and ionisation potential related?
higher penetrating power = lower ionisation potential
as it passes straight by them, does not interact with particles
charges on alpha beta gamma radiation
alpha +2 (helium nucleus)
beta -1 (electron)
gamma = 0
how can you separate alpha beta gamma radiation?
1) pass beam of radiation between positive and negative metal plate
2) alpha attracted towards negatively charged metal plate
3) beta towards positively charged metal plate
4) gamma experiences no deflection
how is the angle of deflection of alpha and beta particles in a magnetic field different?
beta - much greater than alpha (smaller mass)
what is background radiation?
nuclear radiation around us from environment/space
can a radioactive source only emit one kind of radiation?
no, can emit all three types
what does the likelihood of a radioactive source emitting all three sources of radiation depend on?
depends on mass and size of the unstable isotope
bigger/heavier it is, higher likelihood of emitting all 3 types
why are alpha and beta particles highly ionising?
- as they possess a charge
- so they can exert forces of attraction/repulsion on other particles
in what kind of decay does the nucleus of an atom change?
only alpha and beta
- not gamma as nucleus stays same, but only loses energy
how does nucleus change in alpha decay?
- loses 2 protons and 2 neutrons
how does the nucleus change in beta decay?
- neutron number decreases by 1
- proton number increases by 1
as a neutron turns into a proton and an electron
(only electron ejected from nucleus at a high speed)
how does the nucleus of an atom change when gamma radiation is released?
no change, as it only emits energy
if radioactive decay is a random process how can you detect the half life of one?
for a large number of nuclei in a radioactive substance
- you can work out time for half the nuclei to decay
what is the half life of a radioactive substance?
time taken for half the unstable nuclei to decay
what is activity of a radioactive substance?
number of nuclei decay every second
what is used to measure activity of a radioactive substance?
geiger counter
how do you calculate the half life of a radioactive substance on a graph?
see the time taken for the activity to half
why do unstable atoms decay?
in order to become stable
