Radioactive iodine (Iodine-131) has a half-life of 8.04 days. How long will it take for 150g of Iodine-131 to decay until only 25g remains?

The half life of the radioactive element ubtonium-31 is 10 seconds. If 80 grams of unobtanium-31 are initially present, how many grams are present after 10 seconds? 20 seconds? 30 seconds? 40 seconds? 50 seconds?

Radium decomposes at a rate proportional to the present amount. The half life of Radium is 1600 years. If today a radium deposit contains 50g of Radium, determine how much radium is present in the year 2075.

The currently accepted value for the half-life of radiocarbon is 5,730 years. Based on that information, which of the following conclusions is correct. 1. In 2,865 years, the entire original amount of carbon-14 in the sample will be gone. 2. In 11,460 years, the entire sample will be another element. 3. In 5,730 years, half of the original sample of carbon will be gone. 4. In 5,730 years, half of the original amount of carbon-14 in the sample will be gone.