Chapter 8 - Radioactivity Flashcards
Who discovered uranium and when?
Henri Becquerel discovered it in 1896 during a photographic experiment
Who discovered Polonium and Radium?
Pierre and Marie Curie
What are the three types of radioactivity?
Alpha particles α
Beta particles β
Gamma radiation γ
Radiation
The spontaneous breaking up of unstable nuclei with the emission of one or more types of radiation emitted from the nucleus of the unstable atom
What is the composition of alpha particles?
Groups of two protons and two neutrons stuck together (same as a helium nucleus). They have a +2 charge
Describe the penetrating power of alpha particles
They are heavy so have a low penetrating power and are stopped by a few centimetres of air or a sheet of paper
Give a use of alpha particles
americium-241 in smoke detectors
How are beta particles formed?
When a neutron in an unstable nucleus splits into a proton and an electron and the electron is released. They are simply fast moving electrons
Describe the penetrating power of beta particles
They are lighter so travel faster than alpha particles. They can penetrate up to about 5mm of aluminium
Give a use of beta particles
carbon-14 used in carbon dating
What is gamma radiation?
High energy electromagnetic radiation released by an unstable nucleus to expel excess energy. Doesn’t consist of charged particles so is not deflected by electric/magnetic fields
Describe the penetrating power of gamma rays
Very high penetrating ability and is only stopped by a thick slab of lead or concrete
Give a use of gamma radiation
cobalt-16 is used in cancer treatment
What instrument is used to detect radiation?
Geiger-Müller tube (Geiger counter)
Nuclear reaction
Process that alters the composition, structure or energy of the atomic nucleus
What are the differences between a chemical reaction and a nuclear reaction?
- Chemical reaction involves electrons; nuclear reaction involves the nucleus
- No new element is formed in a chemical reaction; a new element is formed in a nuclear reaction
- There is no release of nuclear radiation in a chemical reaction; nuclear radiation is released with a nuclear reaction
- In a chemical reaction chemical bonds are broken and formed; in a nuclear reaction there is no chemical bond breaking or formation
Transmutation
The transformation of one element into another
What happens when an atom loses an alpha particle?
It changes into an atom of the element two places before it in the Periodic Table, and the mass number of the parent atom decreases by four
What happens when an atom loses an beta particle?
It changes into an atom of the element one place after it in the Periodic Table but the mass number of the parent atom stays the same
What happens when an atom loses gamma radiation?
No new atom or element is formed, only energy is lost from the atom
Half-life
The time taken for half of the nuclei in any given sample to decay
What is the half life of carbon-14?
5700 years
What is the half life of cobalt-60?
5 years
What is the half life of polonium-234?
0.15 miliseconds
Radioisootpe
Radioactive isotope
What are the medical uses of radioisotopes?
○Gamma rays penetrate the body and kill cancerous cells → radiotherapy
○Gamma rays are used to sterilise medical equipment by destroyed germs
What are the archaeological uses of radioisotopes?
○Radiocarbon dating
○e.g Dead Sea Scrolls, 2000 years old
Radiocarbon dating (carbon dating)
Technique used to determine the age of an object containing carbon. It is based on the ratio of carbon-14 to carbon-12 in the object
What are the agricultural uses of radioisotopes?
○Used as trackers for the uptake of fertilisers → tracer studies
What are the food uses of radioisotopes?
○Food irradiation
○Gamma rays kill bacteria which cause food to go off
What are the industrial uses of radioisotopes?
○Leaks in pips are located by feeding a radioactive isotope through the pipe
○Test the ground above with a Geiger counter
Give examples of radioactivity around us
○Rocks in the crust decay to release radioactivity
○Radon gas comes from the decay of Uranium or Thorium
○Plants take in radioactive material from the soil
○All called natural radioactivity or background radioactivity
○Nuclear weapons/accidents
