isotopes Flashcards
define isotopes
atoms of same elements which have the same atomic number but different mass number
only some are radioactive/unstable
define radioactive isotopes
some isotopes have unstable nuclei where they emit particles and radiation from that nuclei
when they emit particles they become more stable
carbon-14 dating what is its main use
to date organic remains from archaeological sites (fossil) and give approximate time of death
radiotherapy
rapidly dividing cells like cancerous growths are particularly sensitive to damage by radiation
can be controlled or eliminated by irradiation area containing growth with external or internal radiation
irradiation can be carried out using gamma beam from radioactive cobalt 60 source
how is carbon 24 dating done
living organisms exchange carbon dioxide with air
their bodies has same proportion as carbon dioxide as air at time of death
c 14 starts to decay therefore by comparing levels of c 14 in a fossil to level of c 14 in the air
time of death can be estimated
OR
all living organisms contain carbon 14b and carbon 12 in the specific ratio by mass which is the same as atmosphere
when an organism dies no new carbon 14 molecules metabolised there ratio is at a maximum
since c 14 decays away at a constant and predictable rate the age of specimen can be determined by comparing the present ratio to expected ratio of that organism when living
explain radiotherapy
rapidly dividing cells, like cancerous growths, particularly sensitive to radiation
can be controlled or eliminated by irradiation area containing growth with external or internal radiation
define external radiation
can be carried out using a gamma beam from a radioactive cobalt 60 source
define internal radiation
involves injecting a radioactive isotope usually a gamma or beta emitter into target area
iodine 131 for thyroid cancer
iridium 192 implants for head and breast cancer
what can radiotherapy also be used for
treatment in leukemia to kill off defective bone marrow before bone marrow transplant
to relieve pain with radioactive isotopes
stronium 89 and rhenium 186
what are tracers used for
used in medical field as diagnostic tool
generally short lived and as they pass through body emit gamma rays which can be observed using special apparatus
allowing physician to observe functioning of specific apparatus allowing the physician to observe functioning of specific organs
what are the isotopes used in tracers
molybdenum 99 used to image skeleton and heart muscle in particular but also brain and other organs
chromium 51 used to label red blood cells
iodine 131 used for imaging thyroid