Radioactivity Flashcards
define isotope
atoms of the same element- have the same number of protons but different numbers of neutrons
how does ionisation occur
gain or loss of electrons
what is radioactive decay
as some isotopes are unstable they try and emit particles from the nucleus to stabilise
decay is random and spontaneous
3 types of ionising radiation
alpha, beta, gamma
what is an alpha particle
2 protons and neutrons - He nucleus
what happens when a nucleus emits an alpha particle
Ar falls by 4, atomic number falls by 2
what is a beta particle
emission of an electron
changes a neutron into a proton
what happens when a nucleus emits a beta particle
Ar has no change
atomic number increases by 1
what is gamma radiation
an atom decays by emitting a gamma ray
what happens when a nucleus emits gamma radiation
releases energy- no change to Ar or atomic no
relative penetrating abilities of alpha, beta and gamma
alpha- lowest, blocked by skin/ paper, cannot travel far
beta- moderate, blocked by thin aluminium foil
gamma- highest, blocked by thick lead walls
relative ionising abilities of alpha, beta and gamma
alpha= least
beta= moderate
gamma - most
dangers of ionising radiation
irradiation- exposure to the source but not in contact. therefore if object is moved away from source, damage is stopped
uses of ionising radiation
treating cancer (radiotherapy)
sterilising medical equipment
detecting tumours
activity of radioactive sources
the rate at which a source of unstable nuclei decays measured in decays per second. The unit for activity is the Becquerel (Bq)
half life
measures the time it takes for a given amount of the substance to become reduced by half as a consequence of decay
what does 1 Bq mean
1 Bq = 1 decay per second.
nuclear fission
when heavy weight nuclei split to form smaller weight nuclei
caused by the absorption of neutrons
how does fission cause chain reactions
neutrons released from one reaction collide w/ other atoms causing fission to occur
give an example heavy atom used in fission
Uranium 235
fission produces Barium and krypton
nuclear fusion
when 2 lightweight nuclei fuse to form 1 heavy weight nucleus
releases energy
fusion of H to form He
1) 2H+ fuse to form to from hydrogen 2 isotope, positron and neutrino
2) H+ and hydrogen fuse to form helium 3 isotope, gamma ray and energy
3) 2 helium-3 isotopes fuse to form helium and 2 hydrogen nuclei
why does fusion need high temperatures
to overcome the electrostatic repulsion of positive nuclei
potential use of fusion
would act as a renewable energy source, infinite resource
state which isotopes are formed from the fission of Uranium 235
Barium 141
Krypton 92
