1. Chapter 18

2.  Mass # Symbol  Element Name or symbol – Mass #  Parts of a Reaction Reactants  Products

3.  Alpha emission or decay (  ) –helium atom 4 2 He  238 92 U  4 2 He + 234 90 Th  Beta emission or decay (  )– 0 -1 e in the products  234 90 Th  234 91 Pa + 0 -1 e  Gamma emission or decay (  ) - 0 0   238 92 U  4 2 He + 234 90 Th + 0 0 

4.  Positron emission or decay - 0 +1 e  22 11 Na  0 +1 e + 22 10 Ne  Electron capture – beta particle in the reactants  201 80 Hg + 0 -1 e  + 201 79 Au  Neutron emission or decay– 1 0 n  209 84 Po  1 0 n + 200 84 Po  Proton – 1 1 H or 1 1 p

5.  Mass # and the atomic # totals must be the same for reactants and the products.  39 19 K  35 17 Cl + ___  206 82 Pb  0 -1 e + ___  238 94 Pu + ___  4 2 He + 235 92 U

6.  Alpha decay of Cu-68  Gamma emission of Thorium-235  Positron emission of P-18  Astatine-210 releasing 3 neutrons  Electron capture of Ti-45

7.  Radioactive isotopes or nuclides all decay because they are unstable, some just breakdown much faster than others  Half-life – amount of time for half of the original sample to decay  For two samples of the same isotope, regardless of the sample size, after one half- life, only half of the original amount of sample remains.

8.  IsotopesHalf-Live  Carbon – 145730 years  Sodium – 2415 hours  Bismuth – 21260.5 seconds  Polonium – 215 0.0018 seconds  Thorium – 23075400 years  Thorium – 23424.1 days  Uranium – 2357.0 x 10 8 years  Uranium – 2384.46 x 10 9 years

9.  Barium – 139 has a half-life of 86 minutes. If you originally have a 10 gram sample of Barium-139, how much will be left after 258 minutes? 

10.  How many days will it take 50 grams of Radon – 222 (half-life of 3.82 days) to decay to 3.125 grams?

11.  If a sample of Cesium-135 decays from 10 grams to 2.5 grams over a period of 84 days, what is the half-life of Cesium-135?

12.  238 U  234 Th  234 Pa  234 U  α β β  234 U  230Th  226 Ra  222 Rn  218 Po  214 Pb  α α α α α 214 Pb  214 Bi  214 Po  210 Pb  210 Bi  210 Po  206 Pb  β β α β β α

13.  Henri Becquerel 1852- 1908 Discovered Natural Radioactivity - Nobel Prize (physics) 1903  Wilhem Roentgen 1845- 1923 Discovered X- rays (1895) - Nobel Prize (physics) 1901  Marie (Sklowdowska) Curie 1867 – 1934 Discovered Radium and Polonium - (2) Nobel Prizes (physics) 1903, Chemistry (1911) – first woman to teach at the Sorbonne in its 650 yr history, first person to receive two Nobel prizes, only person to receive 2 Nobels in Sciences

14.  Pierre Curie 1859- 1906 Nobel Prize (physics) 1903  Ernest Rutherford 1871- 1937 Demonstrated the existence of the nucleus Nobel Prize (chemistry) 1908

15.  Cancer Radiation Treatment  Computer Imaging techniques  Radiocarbon dating  Smoke detectors  Food irradiation  Radioactive tracers – Iodine 131 used to treat thyroid illnesses and Thallium -201 can be used determine the damage done to someone’s heart by a heart attack

16.  Nuclear fission was discovered in late 1930’s when U-235 was bombarded with neutrons and observed to split into two lighter elements.  1 0 n + 235 92 U  92 36 Kr + 141 56 Ba + 3 1 0 n  Energy from combustion of 1 mole of U-235 produces 26 million times as much energy as the combustion of 1 mole of methane.

17.  The neutrons are produced from fission reactions, will then react with other radioactive atoms, which will produce more neutrons and so on, potentially creating an uncontrollable chain reaction.

18.  If reaction produces < 1 neutron on average, the nuclear fission stops over time.  If reaction produces exactly 1 neutron for each fission, the process is self-sustaining and is said to be critical.  If reaction produces > 1 neutron from each fission than the process can get out of control very quickly and cause a violent explosion.

19.  Critical mass = mass of fissionable material needed to keep fission reaction going, but at a safe level.  Hiroshima and Nagasaki bombs in 1945 were fission bombs where two subcritical masses were combined and have an extremely rapid fission reaction that causes a huge explosion.

21.  Fusion – combining two smaller nuclei into one heavier, more stable nucleus. 3 2 He + 1 1 H  4 2 He + 0 1 e  Fusion reaction produce more energy than fission reactions.  Fusion reactions are most commonly seen in stars.

22.  We have many potential sources for fusion reactions, but the problem lies in trying to slam two positively charged nuclei together with enough force to make them combine.  It is thought that the temperature must be over 40 million Kelvin for this to occur, which is where the speed of the particles could potentially overcome the repulsive forces.

24.  Somatic damage – done to the organism itself, resulting in either sickness or death.  Effect of somatic damage may be immediate or take years to show their effects, such as radiation treatment for cancer patients.  Genetic damage – damages cells which can be passed on to afflict offspring of initially effecting organism.

25.  Energy of radiation – higher energy = more damage (big surprise)  Penetrating ability of the radiation – gamma particles are high penetrating, beta can penetrate 1 cm and alpha particles can be stopped by the skin.