Isotopes and Radioactivity

Ask questions about projects relating to: aerodynamics or hydrodynamics, astronomy, chemistry, electricity, electronics, physics, or engineering.

Moderators: AmyCowen, kgudger, bfinio, MadelineB, Moderators

Locked
LazyPerson101
Posts: 1
Joined: Fri Sep 11, 2020 10:28 am
Occupation: Student

Isotopes and Radioactivity

Post by LazyPerson101 »

Iodine-131 has a half-life of 8 days. If the amount of iodine-131 in the original sample is 8 g, how much iodine-131 will remain after 24 days?
cmpayne
Former Expert
Posts: 38
Joined: Fri Sep 11, 2020 12:37 pm
Occupation: Expert
Project Question: I'm here to help you find answers science questions and point you in directions to learn more.
Project Due Date: N/A
Project Status: Not applicable

Re: Isotopes and Radioactivity

Post by cmpayne »

Dear LazyPerson101,

Wow! This is a tough question for middle school science!

You can think of half-life as a rate. Half-life is the time it takes for something to reduce in value by half. In this case, "something" is the unstable isotope, the "value" is mass. In other words... The half-life of Iodine-131 is 8 days. Say you have X grams of Iodine to begin with. After 8 days, you will have 1/2 of X grams left.

In your question, the total time of the experiment (24 days) will mean multiple half-lifes will have elapsed. At the start of second 8-day period, you now have 1/2*X grams of Iodine-131, which will reduce by half over the next 8 days. Now, after 16 days of your experiment, you have 1/2 of 1/2*X grams or 1/4*X grams remaining.

The material will continue to decay at this rate (losing 1/2 of it's value every 8 days) during the third/final half-life of your 24 day experiment.

If you are interested in learning more, there are a ton of great resources available. You can google terms like "radioactive decay," "exponential decay," or "half-life" to find them.

Best of luck!
Dr. Payne
Locked

Return to “Grades 6-8: Physical Science”