Determining the Half-Life of Coinium

Name ______Hour ______Date ______Determining the Half-life of coinium

Background: The half-life of a radioactive element is the time it takes for half of its atoms to decay into something else. For example, iodine-125 (I-125) has a half-life of about 60 days. Therefore, in 60 days, 1 g of I-125 will turn into half a gram of I-125 and half a gram of something else (the radioactive decay products of radium). After another 60 days have elapsed, only a ¼ of the original 1g of I-125 will remain (half of the first half).

Purpose: To determine the half-life of the element Coinium.

Materials:  sample of Coinium isotopes (heads represents still radioactive)  1 small beaker as your “shaker”  Data Table  Sheet of graph paper

Procedure: 1. Count the number of Coinium atoms as you place them in the beaker. You should have at least 25 but no more than 30. Record the total number of radioactive atoms you start with in your data table. 2. Cover and gently shake the beaker. 3. Carefully pour your atoms onto your desk/table. You will see that several of the previously radioactive atoms in the group have decayed and the tails is now visible. This means that they are now considered “safe”, or no longer radioactive. 4. Remove and count the atoms that are still radioactive from this shake. 5. Now, continue this process, counting the atoms that are still radioactive, until no more radioactive isotopes remain. REMEMBER: HEADS MEANS IT IS STILL RADIOACTIVE!

Analysis: Construct a graph of N (number of radioactive isotopes left) as a function of the number of shakes. Number of shakes should go on the x-axis and the amount left (N) should go on the y-axis.

Questions:

1. How is this a good model of a radioactive isotope?

2. How is this not a good model of a radioactive isotope?

Shake # Trial #1 Trial #2 Trial #3 Average Radioactive Radioactive Radioactive