Unstable Nuclei and Radioactive Decay

History Alchemy Arose in the Persian empire The study of changing one substance into another Goal to obtain immortality and ultimate knowledge

Nuclear reactions involve a change in the nucleus of the atom Changing one substance into another

Radioactivity Chemical rxns involve a change in the e- configuration of an element No change in the nucleus of the element Some substances spontaneously emit rays and particles (radiation) Cause a change in the identity of the atom Unstable systems By releasing energy become more stable Radioactive decay – unstable nuclei lose energy by emitting radiation

Types of Radiation Alpha radiation Beta Radiation 2+ charge 2 p+, 2 n0 Symbol 42He a 22688Ra  22286Rn + 42He Beta Radiation 1- charge 1 e- Symbol 0-1b 146C  147N + 0-1b

Types of Radiation (….Continued) Gamma Radiation AKA gamma rays NO MASS High energy Symbol 00g Usually accompany alpha and beta radiation Alone don’t make a new particle 23892U  23490Th + 42He + 200g

Nuclear Stability Stability is based on ratio of n0 to p+

Amountf= (Amounti) (1/2)t/T Half Life Time it takes for half a radioisotope’s nuclei to decay into it’s product Amountf= (Amounti) (1/2)t/T T = half life t= time elapsed