1. Ch. 25 Nuclear Chemistry Reactions involving the nucleus of the atom.

2. Radiation Radiation: penetrating rays and particles emitted by a radioactive source. Radioisotopes: radioactive isotopes Why is an atom radioactive? –The nucleus is unstable. Wrong ratio of p:n –Nuclear forces v. Electromagnetic Repulsion

3. Nuclear Stability Graph

4. Types of Radiation Alpha: Helium nucleus emitted from nucleus. Results in less p and n Beta: High speed electron ejected from the nucleus –n → p + e - Gamma: high energy photon

5. Summary of Radiation

6. How far will it go?

7. Alpha Decay

8. Beta Decay

9. Gamma Radiation

10. Gamma Ray on Electromagnetic Spectrum

11. 25.2 Half life

12. Nuclear Stability Graph Red band=1:1 n:p ratio Blue band: stable n:p ratio for isotopes Falling outside this band =unstable

13. The n:p ratio determines the type of decay that will occur Too many neutrons: beta emission (n→p+e - ) Too few neutrons: positron emission (p→n) Too many p and n: alpha emission

14. Examples

15. Half-life A half-life (t 1/2 ) is the time required for one- half of the nuclei of a radioactive sample to decay to products After each half-life, half of the existing radioactive atoms have decayed into atoms of a new product

16. Half-lives can vary in length depending on the isotope. Some last nanoseconds, some last billions of years Decay of U-238:

17. What determines the type of decay a radioactive isotope will undergo? A radioactive sample has a half life of 4 day. How much of a 20 g sample will be left after 4 days? 8 days? 20 days? A radioactive sample has a half life of 5 hours. How much of a 150 g sample will be left after 25 hours?

18. Ch. 25.3 Fission v. Fusion

19. ●Transmutation: the conversion of an atom of one element to an atom of another element ○Can occur by radioactive decay, or when particles bombard the nucleus of an atom ●Elements in the periodic table with atomic numbers above 92 are called transuranium elements. ○These all undergo transmutation ○All are man-made (not found naturally)

20. Fission vs. Fusion Splitting of large nuclei into smaller Releases lots of energy (10 6 times a chem rxn)(E=mc 2 ) Occurs in nuclear power plants Atomic bomb Combining smaller nuclei into larger ones Releases even more energy than fission (3-4 times greater) Occurs in sun/stars H-bomb, thermonuclear bomb

21. Fission reaction

22. Fusion

23. Nuclear power plant Nuclear power plants are sites of controlled nuclear chain reactions!

24. Nuclear Power Plant

25. Control Rods: Cadmium (Cd): absorb n 0 Moderator: water or graphite: slow n 0 Fuel: U-235 Nuclear Waste – Spent rods are stored in water tanks to cool and protect from radiation for many years.

26. Detection Film badge: photographic paper that gets exposed. Used only to monitor, not detect Geiger Counter: gas filled tube to detect radiation through audible clicks Scintillation Counter: phosphor-coated surface that produces flashes of light when exposed to radiation

27. Uses of Radiation Smoke detectors: Americium-241 Food irradiation: Cobalt-60 (gamma) Radioactive tracers to: –Study processes in plants (P-32) –Diagnose medical conditions Thyroid disorders: Iodine-131 Bone scans: Te-99 Medical treatment: cancer