Nuclear Force

Radioactivity The breakdown or decay of unstable nuclei in an attempt to form more stable nuclei. Isotopes are radioactive when, for whatever reason, the attraction b/w p + & n o is insufficient to hold the nucleus together in its existing state. Isotopes that are radioactive are called radioisotopes. Isotopes that are not radioactive are called stable isotopes.

3 types of radioactive decay  : 2p + s & 2n o s – a He nucleus  : e- lost from a n o  : gamma rays – very high energy light

3 types of radioactivi ty  : 2p + s & 2n o s – a He nucleus  : e- lost from a n o  : gamma rays – very high energy light 3 contributing factors to radioactivity 1.Nuclear size  lim F n 2.Ratio of n o /p + 3.Instability of nuclear E levels

Nuclear E levels What evidence is there for nuclear E levels? Hint: E conservation Do you know what the evidence for atomic E levels is?

238 U decay series What does the word “series” mean? Ultimate product of U-238 series is Pb-206. Pb-206 is the only stable product in the U-238 decay series. There are many intermediate products in the U-238 decay series.

Half-life The time it takes for half of a radioactive sample to decay. Radioactive decay is an exponential function.

Exponential decay formula a n = a o e kt a n = final # of moles or atoms a o = initial # moles or atoms e = natural log e kt =.5, since we are dealing with “half”-life k = a constant that varies w/ the half-life of the radioisotope. t = half-life of the radioisotope in question or t = the time of decay

Writing nuclear equations ex. From U-238 decay series Note notation of a n o & e - (  particle)

3 types of nuclear reactions 1.Radioactivity 2.Nuclear fission (p.811 text) 3.Nuclear fusion (paper in text p. 811)

Types of nuclear reactors 1.Light-water : U Breeder : U-238 (paper in Concepts)

Radioactive dating U-238: used for dating rocks How it is done. C-14: used for dating fossils How it is done.