Nuclear Chemistry CHEM 2124 – General Chemistry II Alfred State College Professor Bensley

Learning Objectives  Learn the nuclear symbols for various radioactive particles and forms of energy.  Write a nuclear equation including deducing the reactant or product of said reactions.  List and predict the various types of radioactive decay.  Determine the product nucleus in bombardment reactions.  State the purposes of a Geiger counter.

Learning Objectives  Define the radioactive decay constant.  Define half-life and calculate half-life from the decay constant.  State the ways in which radioactive isotopes are used for chemical analysis.  Describe how isotopes are used for medical therapy and diagnosis.  Explain the difference between nuclear fusion and nuclear fission reactions and describe applications of each.

Nuclear Chemistry I.Introduction A.Isotopes (Review) B.Radioisotopes C.Types of Radiation 1.Alpha Particle 2.Beta Particle 3.Gamma Rays 4.Positrons

Nuclear Chemistry

II.Half Life (t 1/2 ) - the time it takes for one-half of a radioactive sample to decay

Table 10.2

Radioactive Decay of a g Sample of Iodine-131

Nuclear Chemistry –Mathematical relationship to use when calculating half lives or amount of material left after x half- lives have passed. –Based on natural logarithms (ln) –K = elimination rate constant = M/M 0 = e -KT/t 1/2 ln(M/M 0 ) = -KT/t 1/2 A. Decay Curves

Examples 1 and 2 A radioactive substance has a half-life of 7.5 minutes. If you initially have 100 grams of this material, what mass would remain after one hour? You have a sample of radioactive material that initially weighs 50 grams now weighs only grams after 24 hours. What is the half-life of this substance?

Nuclear Chemistry III.Health Effects of Radioactivity A.Nuclear radiation will damage or kill rapidly dividing cells such as bone marrow, skin, and the reproductive and intestinal systems. B.Food is irradiated, exposed to gamma radiation, to kill any living organism in the food.

Nuclear Chemistry original nucleus new nucleus + radiation emitted IV.Nuclear Reactions A.Radioactive decay B.Nuclear Equations C.Alpha Emission (Decay) - decay of a nucleus by emitting an  particle

Nuclear Chemistry D.Beta Emission (Decay) - decay of a nucleus by emitting a β  particle; 1 neutron is lost and 1 proton is gained.

Nuclear Chemistry E.Positron Emission (Decay) - decay of a nucleus by emitting a positron, β + ; 1 proton is lost and 1 neutron is gained.

Nuclear Chemistry 99m 43 Tc Tc  F.Gamma Emission (Decay) - decay of a nucleus by emitting  radiation. Commonly,  emission accompanies  or β emission.

Nuclear Chemistry G.Nuclear fusion - the joining together of two light nuclei to form a larger nucleus. 2 1 H H 4 2 He 1 0 n +

Nuclear Chemistry H.Nuclear fission is the splitting apart of a heavy nucleus into lighter nuclei and neutrons. It can begin when a neutron bombards a uranium-235 nucleus: U n Kr Ba n 3

Example 3 Complete the following nuclear reactions by filling in the boxes with the appropriate numbers or symbols: Pu  234 U C  14 N U  + 0 e4. 11 B  7 Li Kr  85 Rb

Examples 4 and 5 Write a balanced equation for the β-decay of Phosphorus-32, a radioisotope used to treat leukemia and other disorders. Write a balanced equation for the positron emission of fluorine-18, a radioisotope used for imaging in PET scans.

Technetium-99m

Figure 10.5

23 Focus on Health and Medicine Radioisotopes Used in Treatment

PET Scan showing Reduced Enzyme Levels in Various Body Areas of a Smoker

Nuclear Chemistry V.Modern Nuclear Reactors (Fission) A.Chernobyl (1986) Aerial Picture of Reactor at Chernobyl Following Nuclear Accident in 1986

Chernobyl Interesting Facts

Nuclear Chemistry B.Three Mile Island (3/28/1979)

Nuclear Chemistry C.Fukushima Daiichi (2011)Fukushima Daiichi D.Modern Nuclear Warheads Top – Downtown Nagasaki prior to August, 1945 Bottom – Same Area of Downtown Nagasaki After Atomic Bomb was Dropped