radioactivity Flashcards
who helped to develop the atomic model and their models? in order (5)
- john dalton atoms are tiny spheres that canβt be broken up
- jj thompson atoms are spheres of positive charge with tiny electrons stuck inside (plum pudding)
- ernest rutherfood a positive nucleus surrounded by a cloud of electrons
- niels bohr electrons orbit the nucleus at specific distances called energy levels
- james chadwick the nucleus contains protons and neutrons
describe the current atom model.
a tiny nucleus made of protons and neutrons. its radius is 10,000x smaller than the radius of the atom
most of the atom is empty space.
electrons occupy regions around the nucleus called electron shells.
the radius is around 1x10^-10. probably donβt need to know
what happens if an electron gains or releases electro magnetic radiation?
it moves away from the nucleus. if it receives EM radiation
it moves closer to the nucleus. if it releases EM radiation
what is an isotope?
an element with the regular amount of protons but a different amount of neutrons. giving them a different mass number
what is radioactive decay?
when isotopes release radiation to become stable. they can also release neutrons
what are alpha particles? Ξ±
2 neutrons and 2 protons released from the nucleus. the same as a helium nucleus
what are the properties of an alpha particle? Ξ±
can only travel a few cm in air.
is absorbed by paper.
strongly ionising. because it has a large mass
what are beta particles? Ξ²
a fast moving electron released by the nucleus when a neutron becomes a proton.
what are the properties of a beta particle? Ξ²
can travel a few metres in air.
is absorbed by 5mm of aluminium.
moderately ionising. because it doesnβt weigh much
for every beta particle released a neutron in the nucleus turns into a proton.
what is gamma radiation? Ξ³
electro magnetic radiation released by the nucleus. with a short wavelength
what are the properties of gamma radiation? Ξ³
can travel long distances in air.
is absorbed by thick lead or concrete.
weakly ionising. because it has no mass
what does it mean if radiation is strongly ionising?
the radiation interacts more frequently with what it is passing through meaning it quickly loses energy.
what do nuclear equations show?
nuclear equations show radioactive decay using element symbols.
atom before decay β atom after decay + radiation emitted
what happens to an atoms mass and charge atomic number when an alpha particle is released?
the mass decreases by 4.
the charge atomic number decreases by 2.
what happens to an atoms mass and charge atomic number when a beta particle is released?
the mass stays the same
the charge atomic number increases by 1.
what happens to an atoms charge and mass when gamma radiation is released?
nothing.
gamma radiation is just excess energy from the nucleus
how can you measure how much radiation something is releasing?
use a geiger-muller tube part of a geiger counter which records the count rate. the number of radiation counts reaching the tube per second
what is the half life of a source? of radiation
the time it takes for the amount of radiation released by a source to halve.
what is activity and what is it measured in?
the rate that a source decays in becquerels
1 Bq = 1 decay per second
what happens to the activity of a source every time it decays?
the activity decreases.
what is background radiation?
the low level radiation thatβs around all the time.
what are the sources of background radiation? (3)
- naturally occurring unstable isotopes. in air food building materials and rocks
- cosmic rays from space.
- radiation from human activity such as nuclear explosions or nuclear waste
what is radiation dose measured in?
sieverts. 1 Sv = 1000 mSv
what is irradiation?
simply being exposed to radiation. does not make something radioactive
what is contamination?
when unwanted radioactive atoms get on or into something.
what are the risks of radiation in cells?
- tissue damage.
- mutated cells which divide uncontrollably. cancer
- kill cells completely causing radiation sickness
what are 2 medical uses of radiation?
1.medical tracers. gamma
2. radiotherapy. gamma also
what is nuclear fission?
splitting large unstable atoms into smaller atoms. the nucleus usually has to absorb a neutron to split unless spontaneous fission
how can nuclear fission be used to generate electricity?
energy not transferred to the products of fission is carried away by gamma rays which can be used to heat water to turn turbines and generators.
what are control rods used for? nuclear fission
control rods limit the energy produced by fission by absorbing released neutrons slowing down a chain reaction.
what is nuclear fusion?
joining 2 nuclei to produce a larger nucleus.
how can nuclear fusion be used to generate electricity?
energy is released when 2 nuclei join however we do not yet know how to use this energy.
