Atomic Physics

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  • Created by: rachmhw
  • Created on: 11-04-19 17:33
what are atoms that have an unstable nucleus called?
radioactive
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what is the structure of an atom like?
it has protons and neutrons in the nucleus = positive, electrons in shells around the outside = negative
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what is background radiation?
the ionising radiation that is always around us
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what are the 3 types of ionising radiation?
a-particles, b-particles and y-particles
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why are this radiation called ionising?
because they can ionise (knock electrons out of) atoms that they collide with
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how can we detect ionising radiation?
by using photographic film or with a Geiger-Muller tube connected to a counter or ratemeter
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what charge does a proton have?
+1
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what charge does a neutron have?
null
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what is the proton number?
the number of protons in an atom
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what letter can be used to represent the proton number?
Z
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what is the nucleon number?
the amount of protons and neutrons in an atom
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what letter can be used to represent the nucleon number?
A
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what does the nuclide notation show?
A - nucleon number on top, Z - proton number on the bottom, X as the element
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what is the nuclide?
the kind of atom or nucleus characterised by its number of protons and neutrons
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what is an isotope?
an atom of the same element with a different number of neutrons
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what is an alpha particle?
a positively charged particle, identical to a helium nucleus (2 p and 2 n)
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how far can alpha particles penetrate?
4-10cm of air, stopped by a sheet of paper
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how ionising are alpha particles?
very ionisng
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what is the effect of electric fields on alpha particles?
positively charges, higher mass particles, so deflected towards negative charges
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what is the effect of magnetic fields on alpha particles?
positively charged, so deflected by magnetic fields - deflection is in the opposite direction to beta radiation
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what are beta particles?
a negatively charged particle, identical to an electron
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how far can beta particles penetrate?
about 1m of air, stopped by a few mm of aluminium
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how ionising are beta particles?
medium
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what is the effect of electric fields on beta particles?
negatively charged, low mass particle so deflected considerably towards positive charges
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what is the effect of magnetic fields on beta particles?
negatively charged so deflected by magnetic fields - deflection is greater than for alpha radiation and in the opposite direction
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what are gamma rays?
short-wavelength electromagnetic radiation, electrically neutral
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how far can gamma particles penetrate?
almost no limit in air, intensity greatly reduced by several cm of lead or several meters of concrete
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how ionising are gamma particles?
low
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what is the effect of electric fields on gamma particles?
uncharged, so not affected at all
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what is the effect of magnetic fields on gamma particles?
uncharged, so not affected at all
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describe radioactive emission?
it is a random process so we can't tell which atoms will emit radiation (decay) or when
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what are atoms?
very small particles
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how can we use an experiment to test there is a nucleus?
a-particles are fired at a thin, gold target, most passes through but some deflected = there must be a dense region within the atom (nucleus, where the mass is)
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relative mass of a proton
1
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relative mass of a neutron
1
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relative mass of an electron
0.0005
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what is nuclear fission?
the process of a heavy nuclide splitting into 2 smaller nuclei and releasing a few neutrons when they are hit by a slow-moving neutron
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why is nuclear fission important?
a lot of energy is released, the neutrons that are released can go on to cause additional fission reactions in other nuclides
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what power a nuclear power station?
nuclear fission chain reactions
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what is nuclear fusion?
a process where small nuclei, e.g. hydrogen, join together to make heavier nuclei, e.g. helium
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which produces more energy: fusion or fission?
fusion ; it powers stars
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what is radioactive decay?
when a nucleus emits a, b or y radiation so the nucleus becomes stable
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what happens to the number of protons in alpha or beta decay?
the number changes so becomes a different element
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what happens to the nucleon number/ proton number if an alpha particle is emitted?
n = decreases by 4, p = decrease by 2
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what happens to the nucleon number/ proton number if an beta particle is emitted?
n = does not change, p = increases by 1
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what happens to the nucleon number/ proton number if an gamma ray is emitted?
n = does not change, p = does not change
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why do alpha particles have the highest ionising effect?
they are the larger of the particles emissions so collide with atoms more easily = so have a lower penetrating ability
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why do beta particles have a medium ionising effect?
much smaller particles so don't collide as much = so are more penetrating
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why do gamma rays have the lowest ionising effect?
they lose little energy through collisions with atoms = most penetrating
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what is a half-life of the isotope?
how long a sample will take to lose half its activity
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how to find the half life from a activity -time graph?
on y-axis go down half of activity, across to line and down to x-axis = the time between each half is the half life
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what can radioactive material do to living cells?
cause cells to die or divide abnormally
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what safety precautions can be taken with radioactive materials?
use tongs to handle source, never point radioactive source at living tissue, keep in lead-lined containers, measure background radiation to make sure of no contamination, minimise the time using them, wear rubber gloves
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where are radiative soucres used day-to-day?
in hospitals
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what can people do in hospitals for additional safety measures?
wear lead-lined clothing, monitor exposure by wearing a film badge
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what are uses of alpha particles? why?
in smoke alarms - radiation poses no threat to people but when smoke blocks the radiation the alarm is triggered
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what are the uses of beta particles? why?
to monitor the thickness of paper being rolled - if paper thickness changes, the count rate of beta radiation passing through changes as well
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what are the uses of gamma rays?
to destroy bacteria - to sterilise medical instruments
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what can ionising radiation be used for?
used to destroy tumour cells - particular isotope chosen is dependent on site and size of tumour
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what can radioactive materials be used for?
as tracers to find blockages in underground pipes or blood vessels in the body
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Other cards in this set

Card 2

Front

what is the structure of an atom like?

Back

it has protons and neutrons in the nucleus = positive, electrons in shells around the outside = negative

Card 3

Front

what is background radiation?

Back

Preview of the front of card 3

Card 4

Front

what are the 3 types of ionising radiation?

Back

Preview of the front of card 4

Card 5

Front

why are this radiation called ionising?

Back

Preview of the front of card 5
View more cards

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