Half-Life of Radioactive Elements November 15, 2017 Half-Life of Radioactive Elements Nuclear Chemistry Learning Target: I CAN define half life and apply half life skills to determine the amount of radioactive element left after a number of half life cycles

November 15, 2017 Do Now (4 min) Learning target: I CAN define half life and apply half life skills to determine the amount of radioactive element left after a number of half life cycles Answer on your Do Now Sheet: Using Table N, what is the value of the half-life for Iodine-131? How long would it take for half a sample of Iodine-131 to decay? Learning Target: I CAN define half life and apply half life skills to determine the amount of radioactive element left after a number of half life cycles

announcements November 15, 2017 Lab 6 – due Friday, November 17 Homework – Half life worksheet – due Friday, November 17 Test (nuclear chemistry) – Monday, November 20 Test corrections (periodic trends) – Due next Monday Must follow test protocol (on weebly) Afterschool tutoring: Wednesdays 3 – 4 PM Learning Target: I CAN define half life and apply half life skills to determine the amount of radioactive element left after a number of half life cycles

November 15, 2017 Half life: t1/2 Half life: The time required for one half of the nuclei in a given sample to decay. After each half life the mass of sample remaining is half. Different isotopes have different half lives. Use table N Learning Target: I CAN define half life and apply half life skills to determine the amount of radioactive element left after a number of half life cycles

Common Radioactive Isotopes November 15, 2017 Common Radioactive Isotopes Isotope Half-Life Radiation Emitted Carbon-14 5,730 years b, g Radon-222 3.8 days a Uranium-235 7.0 x 108 years a, g Uranium-238 4.46 x 109 years a Learning Target: I CAN define half life and apply half life skills to determine the amount of radioactive element left after a number of half life cycles

Common Radioactive Isotopes November 15, 2017 Common Radioactive Isotopes Learning Target: I CAN define half life and apply half life skills to determine the amount of radioactive element left after a number of half life cycles

November 15, 2017 Radioactive half life After one half life there is 1/2 of original sample left. After two half-lives, there will be 1/2 of the 1/2 = 1/4 the original sample. Learning Target: I CAN define half life and apply half life skills to determine the amount of radioactive element left after a number of half life cycles

Try it yourself! (1 min) What fraction of a radioactive sample would be left after 4 half-lifes? Original amount  first half life  second half life  third half life  fourth half life 1  ½  ¼  1/8  1/16 There is 1/16 of the original sample left after 4 half lifes Learning Target: I CAN define half life and apply half life skills to determine the amount of radioactive element left after a number of half life cycles November 15, 2017

Graph of Amount of Remaining Nuclei vs Time November 15, 2017 Graph of Amount of Remaining Nuclei vs Time A Learning Target: I CAN define half life and apply half life skills to determine the amount of radioactive element left after a number of half life cycles

Half life: Example problem November 15, 2017 Half life: Example problem You have 100 g of radioactive C-14. The half-life of C-14 is 5730 years. How many grams are left after one half-life? Answer:50 g How many grams are left after two half-lives? Learning Target: I CAN define half life and apply half life skills to determine the amount of radioactive element left after a number of half life cycles

Half life: Example problem November 15, 2017 Half life: Example problem If 80 g of a radioactive sample decays to 10 g in 30 min what is the element’s half life? HINT: what is the initial amount? What is half of that? And half of that? Learning Target: I CAN define half life and apply half life skills to determine the amount of radioactive element left after a number of half life cycles

Using table N example problem November 15, 2017 Using table N example problem How many days will take a sample of I-131 to undergo three half life periods? Learning Target: I CAN define half life and apply half life skills to determine the amount of radioactive element left after a number of half life cycles

Final mass example problem November 15, 2017 Final mass example problem What is the total mass of Rn-222 remaining in an original mass 160 mg sample of Rn-222 after 19.1 days? Learning Target: I CAN define half life and apply half life skills to determine the amount of radioactive element left after a number of half life cycles

Regents questions (15 min) November 15, 2017 Regents questions (15 min) groups of 3 Practice regents-level questions of half-life Must finish at least 15 in class Turn in individual work Remainder due Friday, November 17 Learning Target: I CAN define half life and apply half life skills to determine the amount of radioactive element left after a number of half life cycles

Remainder for homework November 15, 2017 Remainder for homework Complete the remainder of the worksheet for homework – due Friday, November 17 Learning Target: I CAN define half life and apply half life skills to determine the amount of radioactive element left after a number of half life cycles

Exit ticket (3 min) November 15, 2017 On a separate sheet of paper: How long would it take for a 100 g sample of Iodine-131 to decay to 12.5g? Learning Target: I CAN define half life and apply half life skills to determine the amount of radioactive element left after a number of half life cycles