Radioactivity Flashcards
atomic number
number of protons
mass number
number of protons and neutrons
Adding or removing electrons
Ionisation
Isotopes
equal number of protons but different number of neutrons
Isotopes
equal number of protons but different number of neutrons
1 Becquerel (1 Bq)
an emission fo 1 particle/second
Alpha Particles
helium nucleus 4 over 2 HE
5 cm
stopped by paper
nucleus transforms into another nucleus with -4 to the mass number and -2 to the atomic number
Beta particles
Ejected from nucleus when neutron turns into proton and electron
Fast moving electrons 0 over -1 e
many metres
stopped by aluminium sheet mm thick
nucleus transforms into another nucleus with 0 to the mass number and 1 to the atomic number
Gamma ray
A short -wavelength electromagnetic wave
great distances
can only be absorbed by thick lead sheets, cm
no mass or charge
Neutron decay
neutron is lost
nucleus transforms into another nucleus with -1 to the mass number and 0 to the atomic number
Radioactive decay
Random process
half life-
1 half life - 1/2 left
2 half life - 1/4 left
3 half life - 1/8 left
etc
Background radiation
Low amounts of radiation all around -not serious health risk
come from rocks
sun and outer space - cosmic rays
radon gas
Hazards of radiation
ionising radiations
alpha destroys body tissue - most dangerous
Radiation dose measurement
sieverts, Sv
Nuclear fission
The splitting of a large atomic nucleus into two smaller nuclei.
Controlled in a nuclear reactor by boron rods
Can be triggered by a neutron. Triggers other reactions - chain reaction
Nuclear energy
Produced in nuclear fission.
kinetic energy - thermal energy
Moderator purpose
To slow down neutrons that are produced in fission. Nucleus split more easily if neutron is slower
Fuel rods
Made from uranium-238 enriched with 3% uranium-235
Embedded in graphite - moderator
Boron rods
regulate the rate of the production of energy
Absorb neutrons - slows down reaction
Concrete shielding
vital protection for workers
Contains a lot of water. No neutrons through.
Nuclear fusion
Two small nuclei combine or fuse to form a single larger nucleus
Form a 4,2 He nucleus and a neutron is ejected
Gamma ray produced- carries away energy
requires a lot of heat energy to overcome electrostatic repulsion.
Source of energy in stars
Uses of Radioactivity
Medicine - Thyroid gland - radioactive iodine is absorbed
- Most medical equipment is exposed to intense gamma radiation - kills bacteria
- Treatment of cancers - radiation to kill cancer cells.
Industry - radioactive tracers detect leaks - fed into pipe and gm tube detects an increase in radiation levels.
Irradiation and contamination
