radioactivity Flashcards
what are atoms
building blocks of all matter
what do atoms have in the centre
nucleus with electrons orbiting around it
protons
positively charged particles with a relative atomic mass of one unit
neutrons
no charge, and has a relative atomic mass of one unit
electrons
negative charge with almost no mass
ionised
if an atom loses electrons
atomic number
number of protons in an atom
mass number
total number of particles in the nucleus of an atom
isotopes
atoms of the same element that have the same number of protons but a different number of neutrons
why are isotopes unstable
due to imbalance of protons and neutrons
what do unstable nuclei emit
radiation to become more stable
forms of radiation
high energy particle
wave
radioactive decay
process of emitting radiation
what process is radioactive decay
random process
nuclear radiation
when an unstable nucleus decays it emits radiation
types of radiation
alpha
beta
gamma
alpha particles
- helium nucleus
- 2 protons and 2 neutrons
- charge of +2
- can be affected by an electric field
beta particles
- fast moving electrons
- produced in nuclei when a neutron changes into a proton and electron
- charge of -1
gamma rays
- EM waes
- highest energy of EM waves
- no charge
range in air- alpha
few cm
beta- range in air
few 10s of cm
range in air- gamma
infinite
alpha penetration and ionisation
stopped by paper
high
beta penetration and ionisation
stopped by a few mm aluminium
medium
gamma penetration and ionisation
REDUCED by few mm of lead
low
alpha decay
mass number decreased by 4
atomic number decreased by 2
beta decay - explanation
- neutron changes to proton and e-
- electron is emmitted
- proton remains in nuclei
- completely NEW element formed
beta decay
mass no. remains the same
atomic no. increased by 1
gamma decay
mass and atomic number stays the same
neutron emmision
atomic no. no change
mass number decreases by 1
amount of radiation received by a person
dose
measured in seiverts
how to detect and measure radiation
using photographic film
GM tube
photohraphic flim
becomes darker when absorbing radiation.
GM tube
transmits an electrical pulse to a counting machine each time it absorbs radiation
count rate
clicking sound GM tube displays
- the greater the clicks, the more radiation absorbed
background radiation
the radiation that exists around us all the time
background radiation stats
radon gas- 50%
rocks and building materials- 15%
medical- 13%
food- 11%
cosmic rays- 10%
other- 1%
natural sources of radiation
rocks
cosmic rays from space
food
man made sources of radiation
- nuclear weapons
- exposure from medical testing
what decays into radon gas
uranium
cosmic rays from space
- sun emits protons
- enters atmosphere at high speed
- collide with air molecules
carbon-14
- organic matter contains this
radiactive activity
the rate at which the unstable nuclei from a source of radiation decays
what is activity measured in
becquerels (Bq)
decreasing activity
- decreases with time
half life
the time it takes for the number of nuclei of a sample of radioactive isotopes to decrease by half
how to calculate half life
- meausre original activity
- determine half-life of original
- measure how activity changes over time
smoke detectors
- alpha radiation normally ionises the air creating a current
- alpha emitter is blocked when smoke enters
- alarm is triggered by a microchip when the sensor no longer detects alpha
what is used to measure the thickeness of thin materials
beta particles
why is beta particles used to measure thickness
- partially absorbs the material
why cant alpha be used to measure thickness
all of the particles would be absorbed and none would get through
radiotheraphy
treatment of cancer using radiation
radiotheraphy method
- gamma rays directed at cancerous tumour
- tracer used to track movement of substances in blood
- PET scan detect emissions from tracer to diagnose cancer and determine location
why is gamma used to sterilise
- most penetrating
- irradiate all sides
- can sterilise without removing packaging
contamination
unwanted presence of materials containing radioactive atoms on other materials
common cause of contamination
radiation leak
irradiation
process of exposing a material to radiation
why is irradiation harmful
kills living cells
what is irradiation used for
method of sterilising
source of irradiation
danger is from radiation emmitted OUTSIDE the object
prevention of irradiation
using shielding such as lead clothing because it abosrbs radioactive material
source of contamination
radiation emitted WITHIN the object
prevention of contamination
prevented by safe handling of sources and air tight safety clothing because it prevents atoms from getting inside
radiation on living cells
causes mutations or can kill cells, can from tumours
acute radiation exposure
skin burns, reduce WBCs
handling material
use tongs
wear protective clothing
shielding
limit time used for
disposure of radioactive waste
buried underground to prevent being released to environment
