Isotopes and Radioactivity
Posted: Fri Sep 11, 2020 10:29 am
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?
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