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what is radioactivity?
the spontaneous breaking up of unstable nuclei with the emission of one or more types of radiation
what are the 3 types of radiation?
alpha particles
beta particles
gamma radiation
what structure does an alpha particle have?
2 nucleus and 2 protons (same as a helium nucleus)
what type of radiation can be represented as 42He ?
alpha particles
what type of charge does an alpha particle carry?
double positive charge
why are alpha particles slow moving?
because they have a large mass
what are the origins of alpha particles?
they are released (thrown out) from unstable nucleus so it may become more stable
why can alpha particles not pass through a sheet of paper?
they have low penetrating power
what are beta particles?
fast-moving electrons
what type of radiation can be represented as 0-1 e ?
beta particles
what is the origin of beta particles?
formed when a neutron in an unstable nucleus is converted to a proton and electron. The beta particle is ejected from the nucleus
why are beta particles faster moving than alpha particles?
they have a smaller mass
what material can stop a beta particle?
a 5cm3 block of aluminium
what is gamma radiation?
high-energy electromagnetic radiation
what speed does gamma radiation travel at?
speed of light
what is different about gamma radiation from other 2 types?
does not consist of charged particles and are not deflected in magnetic or electric fields
what is the origin of gamma radiation?
unstable nucleus emits gamma radiation to lose surplus energy
how much penetrating power does gamma radiation have?
extremely high
what material can stop gamma radiation?
thick slab of lead
how dangerous is gamma radiation?
most dangerous of 3 radiation types
if absorbed can cause cancer
what is a use of gamma radiation?
radio therapy for cancer patients
what is a nuclear reaction?
a process that alters the composition, structure or energy of an atomic nucleus
compare a chemical and nuclear reaction
chemical reaction
involves electrons rather than nucleus
no new element formed
no release of nuclear radiation
chemical bonds broken and formed
nuclear reaction
changes take place in nucleus and electrons not involved
new element formed
release of nuclear radiation
no chemical bond breaking or forming involved
what happens when an atom loses a beta particle?
new element formed has one less neutron and one more proton.
mass number stays same, atomic number increases by 1
what happens when atoms lose gamma radiation?
energy lost from nucleus but does not give rise to new elements
what is transmutation?
the changing of one element to another
what is the half-life of an element?
the time taken for half of the nuclei in any given sample to decay
how is half-life measured?
geiger-muller tube and ratemeter
do temperature and pressure effect the half-life of an element?
no
what is an archaeological use of radioactivity?
radiocarbon dating
what is the half-life of Carbon-14?
5730 years
what is radiocarbon dating?
a technique used to determine the age of an object containing carbon. It is based on ratio of carbon-14 to carbon-12 in the object
by what type of radiation does carbon-14 decay?
beta radiation
what are 2 medical uses of radioactivity?
radiotherapy and sterilising medical instruments
what is radiotherapy?
use of gamma rays to penetrate the body and kill cancerous cells.
