P8 Flashcards
Describe the structure of an atom
Nucleus -> protons and neutrons
Electrons surround nuclei
What are the properties of electrons, protons and neutrons?
Proton:
Positive charge
1 amu
In nucleus
Neutron:
Neutral
1 amu
Nucleus
Electron:
Negative charge
Around 0 amu
Shells orbiting nucleus
What define an element?
The number of protons it has
Number of electrons (ions) and neutrons (isotopes) can vary
What are proton and nucleon number?
(Z) Proton number -> atomic number
(A) Nucleon number -> atomic mass
What is an isotope?
An atom of the same element (same number of protons and electrons) that has a different mass (different number of neutrons)
Different mass
Same proton number (so same element)
No charge
What is a nuclide?
A group of atoms with the same number of protons and neutrons
What is the format of nuclide notation?
A (proton number)
X (element)
Z (nucleon number)
T or F: radioactive emissions are random
True
What causes an unstable nuclei?
Imbalanced forced within the nucleus
Due to:
Large size (more protons than may repel each other)
Too few or too many neutrons
What is radioactive decay? How does it connect to radiation?
An unstable nuclei can emit radiation to become more stable
Reduces the energy -> nucleus more stable
This is radioactive decay
The radiation emitted is referred to as nuclear radiation
What are the characteristics of alpha particles?
helium nucleus -> 2 protons, 2 neutron
Have charged +2
Can be affected by an electric field
Range of a few cm
Can be stopped by paper
High ionisation power
What are the characteristics of beta particles?
Fast moving electron (produced in nuclei -> neutron=proton+electron)
Charge -1
Can be affected by an electric field
Range of a few 10s of cm
Stopped by few mm of aluminium
Medium ionisation power
What are the characteristics of gamma rays?
Electromagnetic waves -> highest energy em waves
No charge
Range -> infinite
Reduced (not stopped) by few mm of lead
Low ionisation power
How do alpha particles, beta particles and gamma particles react to being in a magnetic field?
Alpha -> curve down
Beta -> curve up quickly
Gamma -> no charge, unaffected
Particles only react if they are charged and moving perpendicular to the field
What is ionizing radiation?
Radiation which results in removal of electrons from atoms or molecules
What is the ionizing powers of alpha, beta and gamma (relatively)? Why?
Alpha -> most ionizing (dense trail)
Lose energy quickly, has a short range as a result
Beta -> medium ionizing (medium trail)
Loses energy less quickly, has a longer range, but more penetrating
Gamma -> low ionizing (very not dense trail)
Loses energy slowly, greater range, very penetrating
What is a practical application of alpha particles? Why is it used instead of another type of radiation?
Smoke detectors
Alpha radiation ionizes air -> creates current across gap, completing a circuit (current detected by ammeter) -> smoke fills gap (smoke absorbs alpha particles) -> less or no current is picked up -> ammeter detects -> alarm
Americium-241 used as alpha source
Most ionizing
Least penetrating and doesn’t have a big range
What is a practical application of beta particles? Why is it used instead of another type of radiation?
Measuring thickness
Materials wrong thickness -> amount of radiation out of range -> machine makes adjustments for constant thickness
Beta used because it is partially penetrating
Crack in pipe
Radiation cannot perpetrate the pipe
Crack -> radiation can be detected
Short half life -> doesn’t effect water supplies
What is a practical application of gamma rays? Why is it used instead of another type of radiation?
Radiotherapy (treatment of cancer using radiation)
Radiation kills living cells -> cancer cells are more susceptible rays are directed and moved to minimise harm to the rest of the body
Sterilisation
Sterilize food and medical equipment
Gamma used in both because:
Most perpetrating
What is background radiation?
Radiations that exist around us at all times
Usually just natural radiation, but human activity has increased it
What are the 2 types of background radiation? Give some examples.
Natural: rocks (radon gas (alpha radiation) -> granite or uranium in rocks) , cosmic rays (high speed protons from sun collide with air molecules) , food (usually contact with rocks)
Man made: medical X-rays , nuclear test/fallout/waste/accidents
How is ionizing radiation detected and measured?
Geiger müller tube -> most common instrument to detect and measure radiation
Radiation -> electrical impulses -> counting machine + clicks
Measures in count rates -> decays or counts/s
Other detectors:
Photographic film
Ionisation chambers
Scintillation counters
Spark counters
How can you account of background radiation?
Measure radioactivity without the presence of a radioactive material
Do with radioactive material
Subtract -> correct count rate
T or F: gamma radiation is the only type that changes the atom into a new element
False: alpha and beta change the atom into a different element, gamma doesn’t
