Atoms and nuclear radiation Flashcards
What is an alpha particle?
a helium nucleus
2 protons, 2 neutrons
What is a radioactive substance?
- atoms with unstable nuclei
- number of protons & neutrons is unbalanced
What is radioactive decay?
- emission of radiation (random process)
What is the activity of a substance?
- the rate at which a radioactive substance decays
- measured in becquerels
What can absorb alpha radiation?
- few cm of air
- piece of paper
What are beta particles?
- electrons
- produced when a neutron spontaneously changes into a proton
What can absorb beta radiation?
- thin sheet of aluminium
What is gamma radiation?
- electromagnetic waves
What can absorb gamma radiation?
- thick blocks of lead
What is the symbol for gamma radiation?
Y
What is the ionising power of each type of radiation?
- ionising power = ability to add or remove electrons in uncharged atoms to make them into charged particles
- alpha > beta> gamma
What are the symbols for an alpha particle, beta particle, and neutron?
- 4/2 He
- 0/-1 e
- 1/0 n
What is the half life of a radioisotope?
- the time taken for the number of radioactive nuclei in the substance to halve, or the time it takes for the activity of the substance to halve
What is background radiation?
- a small amount of radiation around us
- due to the rocks in the earth, building materials, air, cosmic rays from the sun and space
How are radioactive tracers used?
- path of the radioactive tracer is tracked through the body or system
- gives useful information about whether or not the body/ system is working correctly
How does radiotherapy work?
- high doses of radiation kills cells
- traget directly at cancer cells
- cancer cells will be destroyed without damaging healthy cells nearby
What is irridation?
- if an object is exposed to a radioactive source
- does not make object radioactive
What is contamination?
- particles of a radioactive substance gets onto or into an object
How do people protect themselves from radiation at their jobs?
- wear a lead apron
- stand behind a lead screen
- wear gloves
- use tongs
Which type of radiation is the most dangerous in contamination?
- alpha
- all energy is absorbed in cell and cannot pass through
Which type of radiation is the least dangerous in contamination?
- gamma
- little energy is absorbed by the cell
- easily passed out of the cell
Which type of radiaton is the most dangerous in irridation?
- gamma
- can pass through the body
What is nuclear fission?
splitting of heavy nuclei into lighter nuclei. this releases a huge amount of energy
what does U-235 split into?
2 lighter nuclei and some neutrons
Describe how bombarding U-235 with neutrons help with increasing the rate of fission
- becomes U-236 (very unstable)
- splits into 2 lighter nuclei, 2-3 neutrons
- gamma radiation produced
What happens in a chain reaction?
- neutrons go on to make other nuclei unstable
- controlled in a nuclear reactor to control the energy released
- nuclear explosion is caused by uncontrolled chain reaction
How is a fission reaction controlled?
- “control rods” (boron/ cadmium) absorb neutrons made from fission so that the chain reaction is reduced
- can be moved further in/ out to control rate of reaction
- all the way in = fission stops (all neutrons absorbed)
- all the way out = fission occurs at highest rate
- graphite moderator slows down neutrons - fission works more efficiently with slower speeds
What is the main problem with nuclear fission?
- lighter nuclei produced is always neutron rich- radioactive
- decays into more stable nuclei - emits radiation
- reactor is surrounded with thick concreate shield to absorb radiation
What is nuclear fusion?
- combining of light nuclei
- the mass of the products of the reaction is always less than the mass of the nuclei that joined together, this “lost” mass is converted into energy
