Isotopes, Radioactivity and Half-Lives

Isotopes, Radioactivity & Half-Lives Learning Target 3.1 1. Complete the table for the following ISOTOPES. Element Vanadium Hyphen Notation Vanadium - 51 Atomic # Atomic Mass # protons # neutrons # electrons 23 51 23 28 23 Vanadium Vanadium-52 23 52 23 29 23 Lead Lead - 209 82 209 82 127 82 Silver Silver – 109 47 109 47 62 47 Nuclear Symbol 51 V 23 52 V 23 209 Pb 82 109 Ag 47 Learning Target 3.4 2. Define Radioactivity. The breakdown of an unstable radioactive isotope’s nucleus to release a decay particle and become a new, more stable isotope/element. 3. There are 4 types of radioactive decay – you need to memorize the particles! Describe the mass, charge, actual identity, and relative penetration power of the following radioactive particles: a. Alpha particles 4 He Large, big charge, blocked by paper 2 b. Beta particles 0 e small, negative charge, blocked by wood/aluminum −1 c. Gamma particles 0 Ɣ small, high energy, no charge, blocked by concrete/very thick lead 0 d. Positron particles 0 e small, positive charge, blocked by wood/aluminum +1 4. For the following problems – write out the entire decay equation. a. Alpha emission by plutonium-239, one of the substances formed in nuclear power plants. 239 4 235 Pu → He + U 94 2 92 b. Beta decay by sodium-24, used to detect blood clots 24 0 24 Na → e + Mg 11 −1 12 c. Oxygen-15 undergoes positron emission, used to assess the efficiency of the lungs. 0 15 O → +1 e + 15 N 8 7 d. Carbon-14 emits beta particles. 14 C 6 0 → −1 e + 14 N 7 e. Thorium-232 goes through alpha decay. 232 4 228 Th → He + Ra 90 88 2 f. Radium-226 emits gamma and alpha particles. 226 Ra → 00Ɣ + 42He + 222 Rn 88 86 g. Chlorine-36 undergoes positron emission. 0 36 36 Cl → e + S +1 16 17 h. Argon-37 is produced by beta decay. 37 0 Cl → −1 e + 37 Ar 18 17 i. Fermium-257 is formed by alpha and gamma emission. 261 0 4 257 No → Ɣ + He + Fm 102 0 2 100 j. An isotope of rhenium-188 undergoes alpha decay. 188 Re → 42He + 184 Ta 75 73 k. A radioactive isotope undergoes beta and gamma decay to produce Chlorine-36. 36 0 36 0 S → Ɣ + e + Cl 16 0 −1 17 l. Radium-226 goes through decay to produce Radon-222. 226 4 222 Ra → He + Rn 88 86 2 m. Lead-208 emits a positron to produce a stable isotope. 0 208 208 Pb → e + Tl +1 82 81 Learning Target 3.5 For the following half-life problems, show all work, include units & round appropriately! 5. One of the radioactive nuclides formed in nuclear power plants is hydrogen-3, called tritium, which has a half-life of 12.26 years. How long before a sample decreases to 1/8 of its original amount? 1 → ½ → ¼ → 1/8 3 half lives x 12.26 = 36.78 years 6. 7. Uranium-238 is one of the radioactive nuclides sometimes found in soil. It has a half-life of 454 years. What percentage of a sample is left after 2270 years? 2270/454 = 5 half lives 100% → 50 → 25 → 12.5 → 6.25 → 3.125 which rounds to 3.13% Cesium-133, which is used in radiation therapy, has a half-life of 30 years. What was the size of the original sample if after 120 years you now have 16.0 grams? 120/30 = 4 half lives need to work backwards 256 → 128 → 64 → 32 → 16 256 rounds to 300 grams 8. 9. Phosphorus-32, which is used for leukemia therapy, has decayed to 1/16th of its original amount in 42.9 days. What is the half-life of phosphorous-32? 1 → ½ → ¼ → 1/8 → 1/16 took 4 half lives 42.9/4 = 10.725 rounds to 10.7 days Iodine has a half-life of 8.07 days. Assuming you start with 90.5 grams, how much of the sample (in mg) would you have left after 24.21 days? 24.21/8.07 = 3 half lives 90.5 → 45.25 → 22.625 → 11.3125g x 1000 mg = 11312.5 rounds to 11300 mg 1g