Topic 6- Radioactivity Flashcards
How much larger is the atom than the nucleus?
10,000
Where is the mass of an atom
In its nucleus
What is the size of an atom vs a molecule
- 10^-10m (0.1nm)
- 10^-9 m (1nm)
What is the atomic number?
Mass of protons
What is the nucleon number?
Mass of neutrons and protons
What is an isotope?
- Same electrons and protons
- Different number of neutrons
- Different mass
What is the relative mass and charge of an electron?
1/2000 (1/1836)
negative
What is the relative mass and charge of a neautron?
- 1
- neutral
What is the relative mass and charge of a proton?
-1
-positive
What is the relative mass and charge of a positron?
-1/2000 (1/1836)
- Positive
What happens to electron orbit when they absorb emissions of electromagnetic radiation?
- Gains energy and becomes excited
- Moves up an energy level, to the next ring (to an unoccupied space)
- Looses energy (form of radiation) and moves back to its ground state
Alpha decay: what happens
- Random unstable nucleus DECAYS/splits into a new less unstable nucleus
- and a Helium nucleus (2 protons and 2 neutrons)
Beta minus decay: what happens
- Unstable isotopes with too many neutrons
- Neutron decays into a proton and electron
- High speed electron cuasing radiation
Beta plus decay: what happens
- Unstable isotopes with too many neutrons
- Positron decays into a neutron and electron
- High speed positron causing radiation
Gamma radiation: what happens
-After alpha or beta decay
- New nucleus is still unstable
- Emits energy as gamma waves
What type of radiation is alpha, beta and gamma?
- ionising radiation
What stops alpha radiation?
- Thin sheet of paper
What stops beta radiation?
- Aluminium (5mm)
- Lead (2-3mm)
What stops gamma radiation?
- Thick lead
- Concreate (1m)
highest to lowest ionising radiation order?
- Alpha
- Beta
- Gamma
What are the natural sources of background radiation?
- Randon gas- decay of uranium and thorium (igneous rocks)
- Internal radiation- Absorb radioactive material (carbon 14 instead of carbon 12)
Artificial sources of background radiation
- Leakages/ accidents of electricity generators that use nuclear energy
- Fall-out with weapons testing
- Accounts for very small percentage
What is background radiation?
Low level radiation present everywhere
What is used to measuring/detecting radiation?
- Photographic film
- Geiger tube and counter
How does the photographic film detect radiation?
- film that changes colour due to radiation
- Mediums placed in front of film to determine the penetrating strength of the (therefore which) radiation
- Open window, paper, lead, concrete
How does the GM detect radiation?
-ionising radiation ionises the gas in the tube
-Free electrons are attracted to the anode
- Their flow creates a circuit
-This produces a clicking sound
How to work out the activity rate of a radioactive substance?
- Count/ time
What is half life?
- The time taken for half the unstable radioactive nuclei to decay
- Or the Activity rate
- to decrease by half
- half life is always the same (just less needs to be decayed to decrease bu half)
e.g 120->60 takes 60 years. 60->30 takes 60 years.
How do we measure half life using a graph?
- Find the half life
- Fine the time it took
- Repeat with the quatre life
- Find the difference between the two
What is the unit of activity rate of an isotope?
- A becquerel
What was the plum pudding model
- Plum pudding, electrons and protons incased in a nucleus
What was the alpha particle scattering experiment and what where the results?
- Alpha particle shot at thin gold foil
- Most went through
- Some were deflected
- Very few where deflected backwards
What did the fact that most alpha particles went straight through the gold foil prove?
- Most of an atom is just empty space
(positive helium nucleus hit nothing most of the time)
What did the fact that some alpha particles deflected slightly/ backwards through the gold foil prove?
- Nucleus is positive
- The positive helium nucleus was repelled by the larger positive nucleus and changed direction
Why was gold foil used in the particle scattering experiment?
- Highly positive
- Electrons in the gold weren’t attracted to the alpha particle
What was Bohr’s atomic model?
- Quantised electron shells
- Electrons orbit a positive (much larger) nucleus
How is alpha radiation deflected in a magnet?
- Positive movement causes a current
(FBI) force pushes it upwards or downwards - Slightly changes movements
How is beta minus radiation deflected in a magnet?
- Deflected more as it has a smaller mass
- Negative movement causes current in the opposite direction (FBI)
How is beta plus radiation deflected in a magnet?
- Deflected more as it has a smaller mass
- Positive movement causes current in the direction (FBI)
What is alpha radiation used for?
-smoke alarms
What is beta radiation used for?
-Tracing and gauging thickness
What is gamma radiation used for?
-Find and treat cancer
-Irridation of food
-Sterilising equipment
How do smoke alarms work
and why is alpha used?
-Alpha radiation ionizes air
-Creates a current
-Smoke disrupts current
Why aplha:
-Highly ionizing (effective)
-Lowly penetrating (safe)
-Long half life= works for long time
How does tracing and guaging thickness work
and why is beta used?
-Beta particles shot through paper
-If too thick less go through
-If too thin more go trhough
Why beta:
-Partially penetrating
-Finds a middle ground for the thickness
How does food irridation/ or sterilising surgical equipment work
and why is gamma used?
-Radiation kills bacteria and fungus and parasites on food
-Extends shelf life
-No need for heat or chemicals
Why gamma:
-Highly penetrating (inside food/ through packaging)
-Lowly ionizing (less dangerouse)
How does diagnosing and treating cancer work
and why is gamma used?
Finding:
-Radioactive tracers emmit gamma rays
Treating:
-Gamma beams concentrated on tumour
-Internal/ digest radioactive material that deliveers high dosage to tumour
Why gamma:
-Highly penetrating (emmit through the body)
-Lowly ionising (less dangerouse to tissue)
short half life- not affect others
How is ionising radiatoin bad?
-Damages/kills cells
-Damages tissue
-Changes DNA cuasing mutations
-Can cause cancer
What are the precuations when working with ionising radiation?
-Minimise exposuree
-Greater distance (inverse square law)
-Protective barriers: paper, aluminium/ plastic, concrete/lead
-Protective clothing e.g lead aprons or full body coverging suits
-Storage: in shielding contains + waste underground
How does half life affect the dangers of ionising?
Shoter:
-Less dangerouse
-Decays more quickly meaning it is less ionising over time
-No.of atom nuclei decrease quickly
-Can be more initially dangerouse
-Use quickly and store securely
Longer:
-More dangerouse over longer periods
-Store undeground and avoid leakages
- Contaminate environments for centuries
Precuations for patients?
-Minimise exposure
-Use shorter half life substances
-Don’t touch contmainated equipment
What is contamination vs Irridation and their hazards?
Contamination:
-Radiactive material inside the body
-Long lasting
-Dont ingest radioactive material
Irridation:
-Radiation exposed to the body
-Temporary, stops when you move away
-Use shielding
What is the two ways tumours are treated?
-internal
-External
How are tumours treated internally?
-Radioactive substance placed in or near tumour
-Ionises and kills it
-Usually alpha or beta- dont travel far so less damage
How are tumours treated externally and why is it used?
-Machine directs high-level gamma beams towards tumour
-Ionises and kills it
-From a linear accelerator
-Gamma used as it can penetrate through the body
Why:
-Used for large or deep tumours (hard to get to internally)
Benefits and problems with treating tumous internally?
Advantages:
-Effectively delivers high doses directly to tumour
-Damages less surrounding tissue
-May be temporary (remeoved after a short period of timee)
Disadvantages:
-Has to be removed
-May be permenant substance (until it decays)
-Can cuase local swelling, infections and discomfort
Benefits and problems with treating tumous externally?
Benefits:
Problems:
-Damages more surrounding tissue
-Cuases skin burns, fatigue and hairloss
-Takes a long time
How do PET scanners work?
-Ingest radioactive substance with glucose (energy needed for tumours so accumlates there)
-Undergoes beta plus decay
-Produces positrons (antiparticle)
-Positrons come into contact with electrons -Cuases annihilatoin
-Cuases gamma rays to be produced
-Scanners detect this and produce a 3D image
How do medical tracers work?
-Ingest substance with carrier (glucose)
-Accumilattion detected e.g PET or by geiger counters
Why are isotopes in PET scanners produced near by?
-Need short half life (less contamination)
-Used quickly
Benefits and problems with nuclear power plants?
Benefits:
-No CO2
-Produces lots of energy
-Reduces dependeency on fossil fuels
Disadvantages:
-Radiation leakes + bad public perception (chernobyl)
-Nuclea waste remains undergound for millenia + difficult to store
-High initial cost and long construction time
-Terrorism risk
What ways can radioactive material be used as an energy source?
-Fusion
-Fission
-Radioactive decay
What is fission?
-Uranum-235
-is split by high speed neutrons
-into two smaller more stable duaghter nuclei
-An 2 or more high speed neutrons
-And a release of energy
duaghter nuclei are still radioactive
Why and how is fission controlled?
-Chain reaction cuases expontential increase in reactions
Control rods:
-Absorb free neutrons (limits number of reactions)
-raised to allow more fission
Modorator:
-Water or graphite slows down neutron speed
-Less energetic (collisions)
How does fission’s heat produce electricity?
-Produces immense heat
-Transferred to different water supply in a heat exchanger
-Produces high pressure steam
-Turns a turbine
-Thermal into kinetic energy
-Conected to a generator
-Generator uses electromagnetic induction to produce a current
-After passing througb turbine steam is cooled and condensed back into the heat exchanger
What is fusion?
-The creation of large nuclei
-From two smaller nuclei
-Looses mass
-Converted into lots of energy (e=mc^2)
energy source of stars
Why does fussion need extreme conditions?
-High temp and pressure
-Overcome electostatic repulsion between two protons
Why is fusion not really economically viable?
-Expensive to keep high temp and pressure
-Machines as humans can’t get close
-Need to maintain plasma in magnetic confinement (artificially confine as we don’t have stars gravity)
nvm
