NUCLEAR CHEMISTRY

1. NUCLEAR CHEMISTRY DO NOW: Answer the following questions What part of the atom do we focus on in nuclear chemistry? List the different types of nuclear emission What is the difference between artificial and natural transmutation?

2. STABILITY OF NUCLEI • Most chemical reactions involve either the exchange or sharing of electrons between atoms. Nuclear chemistry involves changes in the nucleus. • Transmutation is when the nucleus of one element is changed into a different element. • The ratio of the neutrons to protons determines the stability of a given nucleus, thus, the ratio in all nuclei with atomic numbers greater than 83 have unstable nuclei and are radioactive

3. Radioisotopes are elements that are unstable and thus radioactive. • When an unstable nucleus decays, it emits radiation in the form of alpha particles, beta particles, positrons and / or gamma radiation. • An alpha particle is a helium nucleus composed of 2 protons and 2 neutrons; represented by the symbol 24He or 24α and is found in Table O on the Reference Table. STABILITY OF NUCLEI

4. A beta particle is an electron whose source is an atomic nucleus, while a positron is identical to an electron except that it has a positive charge Almost all nuclear decay also releases some energy in the form of gamma rays. Radiation can be harmful when it interacts with living things. STABILITY OF NUCLEI

5. In Alpha decay, a nucleus ejects an alpha particle and becomes a smaller nucleus with less positive charge; it can be summarized as follows: • Atomic # decreases by 2 • # of protons decreases by 2 • # of neutrons decreases by 2 • Mass # decreases by 4 STABILITY OF NUCLEI

6. 11. Beta decay has the effect of turning a • neutronin the nucleus into a proton and an electron; it can be summarized as follows: • Atomic # increases by 1 • # of protons increases by 1 • # of neutrons decreases by 1 • Mass # remains the same STABILITY OF NUCLEI

7. Positron emission is interpreted as the production of a positron during the conversion of a proton to a neutron; it can be summarized as follows: • Atomic # decreases by 1 • # of protons decreases by 1 • # of neutrons increases by 1 • Mass # remains the same STABILITY OF NUCLEI

8. 13. As in chemical equations, mass and • charge must balance on both sides of the equation • (all the top #s on the left must equal the top #s on the right ANDall the bottoms #s on the left must equal all the bottom #s on the right) • LAW OF CONSERVATION!! STABILITY OF NUCLEI

9. 13. As in chemical equations, mass and • charge must balance on both sides of the equation • (all the top #s on the left must equal the top #s on the right ANDall the bottoms #s on the left must equal all the bottom #s on the right) • LAW OF CONSERVATION!! STABILITY OF NUCLEI

10. Write the alpha decay of Au -198 • Write the beta decay of Sr -90 Writing Nuclear Reactions

11. Nuclear reactions can either be naturally occurring or artificial. • Natural transmutations are: alpha, beta, and positron decay that occur as a result of unstable neutron-to-proton ratios and consist of a single nucleus undergoing decay. TRANSMUTATIONS

12. 3. Artificial transmutation is the bombarding of a nucleus with high- energy particles to bring about a change; scientists in research and commercial settings perform artificial transmutations and will have two reactants, a fast particle and a target material. TRANSMUTATIONS

13. 4. There are 2 different types of artificial transmutations; the first type involves the collision of a charged particle with a target nucleus and the second type involves the collision of a neutron with a target nucleus. TRANSMUTATIONS

14. DO NOW: Answer the following questions: • Explain the difference between natural and artificial transmutation • Write the alpha decay of Fr-220 • Write the beta decay of N -16 AIM: What is fission/fusion?

15. 1. A fission reaction involves splitting of a heavy nucleus to lighter nuclei and a fusion reaction involves combining light nuclei to a heavier nucleus. • 2. In both types of reactions, the total mass of the products is less than the total nuclear mass of the reactants. FISSION/FUSION

16. 3. The loss of mass in these nuclear reactions represents a conversion of some matter into energy expressed by Albert Einstein in his famous equation: E = mc2. The mass that has been converted to energy is called the mass defect. • 4. The energy produced by nuclear reactions is far greater than that of chemical reactions. FISSION/FUSION

17. 5. The chemical reaction, decomposition, is similar to fission reactions because one is splitting up into two plus energy. • The chemical reaction, synthesis, is similar to fusion reactions because two are combining into one plus energy. • Examples of each equation: FISSION/FUSION

18. 7. Radioactive substances decay at a constant rate and the number of unstable nuclei that will decay in a given time can be predicted. • 8. Half-life is the time it takes for half the atoms in a sample to decay. HALF LIFE

19. Each isotope has its own half-life. The shorter the half-life of an isotope, the less stable it is. Table N in the Reference Tables give the nuclide, half-life, decay mode, & nuclide name. • STRATEGIES FOR HALF LIFE PROBLEMS HALF LIFE

20. The half life of cobalt – 60 is 5.3yr. How much of a 1.000-mg sample of cobalt – 60 is left after 15.9yr? HALF LIFE - PRACTICE

21. Carbon – 11, used in medical imaging, has a half life of 20.4min. The C-11 nuclides are formed, and the carbon atoms are then incorporated into an appropriate compound. The resulting sample is injected into a patient, and the medical image is obtained. If the entire process takes five half lives, what percentage of the original carbon – 11 remains at this time? HALF LIFE - PRACTICE

22. AIM: Uses and Dangers of Radioisotopes

23. Radioisotopes have many practical applications in industry, medicine, and research but also have potential dangers because of the harm that can be done by the release of radiation. • Carbon- 14 is used in dating previously living materials USES & DANGERS OF RADIOISOTOPES

24. A tracer is any radioisotope used to follow the path of a material. The ability to detect radioactive materials and their decay products makes it possible to determine their presence or absence in a substance. • C-14 and P-31 are tracers and C-14 is used to map the path of carbon in metabolic processes USES & DANGERS OF RADIOISOTOPES

25. Radioactive isotopes and gamma rays are absorbed in varying amounts by different materials and the thicker the material, the more radiation will be absorbed. Radiation products can be used to measure the thickness of plastic wrap or aluminum foil or to test the strength of a weld. USES & DANGERS OF RADIOISOTOPES

26. Certain radioactive isotopes are used in the body as tracers because they have short half-lives and are quickly eliminated from the body. • Thyroid conditions use I-131 to detect and treat because the I-131 accumulates in the thyroid gland, therefore, when a person has an overactive thyroid I-131 can be given in large enough doses to destroy some of the thyroid and reduce its production. USES & DANGERS OF RADIOISOTOPES

27. Co-60 emits large amounts of gamma radiation as it decays and thus can be aimed at cancerous tumors, whereby killing the rapidly growing cells of the tumor than normal cells. • In order to kill bacteria in foods, beams of gamma radiation and the two used to destroy anthrax bacilli are C-60 and Cs-137. USES & DANGERS OF RADIOISOTOPES

28. Cancerous tumors can accumulate Tc-99 and thus is used for detection purposes since it has a short half-life and is quickly eliminated by the body. • Radiation not only destroys unwanted cancerous cells but it also can destroy normal tissue which can cause serious illness, death and can be passed on from generation to generation USES & DANGERS OF RADIOISOTOPES

29. Nuclear power plants are an issue because the waste/decay products have long half-lives which have the potential of being released into the air or water. USES & DANGERS OF RADIOISOTOPES