Radioactivity Flashcards
ion
element that has gained/lost electrons
isotope
element with the same number of protons, but different number of neutrons
Mass number
protons + neutrons
Atomic number
proton number
When does an atom become stable
when it doesn’t emit ionising radiation anymore
Ionising radiation
radiation with the ability to knock electrons off other atoms, damaging them
Alpa particle
2 protons + 2 neutrons (helium nucleus)
charge: +2
mass: 4
slow
most ionising
least penetrating (few cm of air, paper, skin)
Beta particle
electron
charge: -1
mass: 1/1800
fast (10% of speed of light)
medium ionising
medium penetrating (aluminium, bone)
Gamma wave
Electromagnetic wave
Gamma wave
Electromagnetic wave
charge: 0
mass: 0
very fast (speed of light)
least ionising
Most penetrating (Thick lead)
Describe how to measure radioactivity of a rock
- use a GM tube + counter (if not given)
- measure background radiation
- measure radiation from the rock
- subtract background
Describe an experiment to prove a rock emits beta radiation
- use a GM tube + counter (if not given)
- measure background radiation
- measure radiation from the rock
- place PAPER between rock and tube
- reading stays the same
- place aluminium between
- radioactivity drops to background
Sources of Background radiation
Cosmic rays from sun
Potassium in food + drink
Radon gas in air
Radioactive rocks in buildings/mountains
Alpha emission
mass number -4
atomic number -2
U 238,92 –> α 4,2 + Th 234,90
Gamma emission
mass number stays the same
atomic number stays the same
U 238,92 –> γ 0,0 + U 238,92
Beta emission
mass number stays the same
atomic number +1
U 238,92 –> β 0,-1 + Np 238,93
Beta production
During beta emission, a neutron splits into a proton (stays in the nucleus) and an electron (leaves)
Activity
is the amount of raidation given off by an element over a period of time. Measured in Bequerells (Bq)
It is random (unpredictable)
Half life
The time it takes for half of the radioactive nuclei/isotope to decay
Uses of radioactivity
Radiocarbon dating
Radioactive tracers
Radiotherapy
Serilization
Radiocarbon dating
One in a billion carbon atoms is Carbon - 14
Once a plant or animal dies, this carbon 14 is not replaced and it decays over time.
Carbon 14 has a half life of 5700 years.
By measuring amount of carbon -14 in a dead organism we can determine when it died.
Radioactive tracing
Radioactive isotopes (technetium 99) with short half-life can be injected to humans.
Once in blood stream, emits gamma which penetrates the body and can be detected outside.
Isotope follows circulatory system, we can see any problems with heart, arteries or veins.
Same in digestive system
Radiotherapy
High intensity gamma rays to treat cancer.
Placing radioactive isotope near can kill cancer cells.
But can also kill healthy cells nearby
Sterilization
Gamma can be used to sterilize food and medical equipment.
Gamma penetrate food or equipment and kill bacteria on both sides.
