Chapter 4 Chad Stessman
Half-life • Radioactivity is a random process • Half life is time it take half of the atoms of a sample to decay
Half-lives • Tritium-3H- half life of 12.3 years • 238U has a half life of 3.8 billion years • Amount remaining after a certain number of half-lives is 1/2n. Where n= number of half lives
Radioisotope dating • Radioactive decay can be used to determine the age of a sample.
Carbon-14 dating • 14C is an isotope of carbon. • Formed by bombardment of nitrogen in the atmosphere with cosmic rays, neutrons
14C incorporates into living creatures through the carbon cycle • When plant or animal dies, it is no longer incorporating 14C
14C half life is 5730 years • After about 10 half-lives or 50,000 years too little 14C to be effective. • 14C formation not always constant, need to find references
Tritium Dating • 3H has a half-life of 12.3 years • Used to determine age of brandy and wine samples 10-100 years old
Other isotopes used in dating • Potassium-40 1.3x109 years • Rhenium-187 4.3x1010 years • Uranium-238 4.5x109 years
Artificial Transmutation • Middle ages alchemists tried to accomplish transmutation • Nuclear reactions can change atoms
Uses of Radioisotopes • Around 3000 radioactive isotopes can be produced from stable isotopes.
Tracers • Used in physical, chemical or biological systems. • Used to look for leaks, follow reactions, get images of biological processes.
Nuclear Medicine • Radiation Therapy • Diagnostic Uses
Radiation Therapy • Use radiation to destroy rapidly growing cancer cells. • Aim radiation at cancer cells
Diagnostic Uses of Radiation • Radioisotopes are use to image or diagnose problems with the body functioning. • Technium-99m-gives up a gamma ray to become more stable 99mTc 99Tc + gamma