7 Radioactivity and Particles Flashcards
Mass number
Number of protons + neutrons
Atomic Number
Number of protons
Proton Relative Charge
+1
Proton relative mass
1
Neutron relative charge
0
Neutron relative mass
1
Electron relative charge
-1
Electron relative mass
1/2000
Atom
Same number of protons and electrons
Ion
Different number of protons or electrons
Positive or negative
Isotopes of an element
Same number of protons
Different number of neutrons
Ionising Radiation
Produced when an unstable nucleus decays
It is a spontaneous and random process
Alpha Particle
2 protons, 2 neutons = helium nucleus
Alpha decay
2 protons + 2 neutrons (an alpha particle) are ejected from the parent nucleus.
Leaves behind a smaller daughter nucleus + energy
Beta Particle
Electron
Beta Decay
A neutron decays to a proton (remains in the nucleus) and an electron (which is ejected at high speed as a beta particle)
Gamma
Following alpha or beta decay, the daughter nucleus is left in an excited state. So it gets rid of this excess energy by emitting a gamma ray.
Alpha ionising power
High
Beta ionising power
Medium
Gamma ionising power
Low
Alpha penetrating power
Low
Beta penetrating power
Medium
Gamma penetrating power
High
Alpha range in air
5-8 cm
Beta range in air
500 - 1000cm
Gamma range in air
Infinite
Barrier to stop alpha
Paper
Barrier to stop beta
3mm aluminum
Barrier to stop gamma
Thick sheet of lead
What can be used to measure ionising radiation
Photographic Film
Geiger Muller Tube
Measuring ionising radiation: Photographic film
Radiographers work in nuclear plants so they wear a holder containing photographic film (sensitive to ionising radiation)
Periodically is sent for developing ->the darker the film, the more radioactive exposure
Measuring ionising radiation: Geiger Muller Tube
A gas is ionised by any incoming radiation, allowing a small current to flow.
The pulses of current are detected and converted to a count
Uses of Radioactivity in industry + medicine
Thickness monitoring
Non destructive testing
Radioactive decay
Radiotherapy
Medical Tracers
Uses of radioactivity: Radioactive decay
Small amounts of carbon-14 pass in and out of an organism when it dies
This carbon-14 becomes trapped and the radioactive activity decreases -> this activity can be measured to work out the age
Uses of radioactivity: Radiotherapy
Ionising radiation can be targeted at unwanted cells e.g. cancerous cells to kill them
Uses of radioactivity: Medical Tracers
Small amounts of radioactive substances (normally gamma emitters) can be ingested into the human body as tracers.
Gamma - emitters have short half lives.
The radioactivity is detected externally, and help diagnose health problems
Contamination
If a gamma source is wiped on an object, some of the radioactive nuclei are transferred to the object -> the object becomes radioactive
Irradiation
If an object is exposed to a gamma source, it kills bacteria -> the object does not become radioactive
Dangers of ionising radiation
Can ionise atoms in living cells -> can cause mutations, which can cause death
Can damage cells + tissues
Half - lives
The time taken for half the number of original nuclei to decay
The time taken for the activity to half
What can be a source of energy?
Nucleur reactions
Nucleur Fission
- A neutron is absorbed by a Uranium-235 nucleus
- The resulting nucleus Uranium - 236 is radioactive
- Uranium - 236 splits into 2 lighter nuclei (krypton and barium), 3 neutrons, and gamma radiation
- The 3 neutrons cause further fissions = chain reaction
What is fusion the energy store in?
Stars
Conditions for Nuclear Fusion
Only works at high temp. + pressures to cause 2 positive hydrogen isotopes to attract.
Equation for Nuclear Fusion
2 hydrogen isotopes fuse to form a helium nucleus + neutron
The helium nucleus and neutron have a lower mass than reactants due to energy being released.
Parts of Nuclear Fission Reactor
- Control Rods
- Moderator
- Fuel Rods
- Coolant
Nuclear Fission Reactor: Control Rods
Boron
Absorbs neutrons and can be moved in and out of the core.
Nuclear Fission Reactor: Pressure Vessel
Steel + concrete
Stops ionising radiation from escaping
Nuclear Fission Reactor: Moderator
Graphite
Slows down fast moving neutrons so that they are more likely to be absorbed by Uranium - 235
Nuclear Fission Reactor: Fuel Rods
Uranium - 235