Half-Life Calculations

Practice half-life calculations and radioactive decay problems. Solve for remaining amounts with ease!

Use the table to answer these Half-Life questions. A patient is administered 20 mg of iodine-131. How much iodine will remain in the body after 40 days if the half-life is 8 days? Half-Life # 0 1 2 3 4 Time (days) 0 8 16 24 32 Amount (mg) 20 10 5 2.5 1.25 Percent of Parent remaining 100% 50% 25% 12.5% 6.25% Fill in the blanks based on the above table. Based on the table, 0.625 mg of iodine-131 will remain in the body after 40 days. Use a table to answer this half-life question. Technitium-104 has a half-life of 18 minutes. How much of a 100.0 g sample remains after 72 minutes. # of Half-life 0 1 2 3 4 Time (minutes) 0 18 36 54 72 Amount (g) 100.0 50.0 25.0 12.5 6.25 Percent of Parent Remaining 100% 50% 25% 12.5% 6.25% Fill in the blanks using the above table. After 72 minutes, 6.25 g will remain of the technitium-104 sample. If you are not sure how to do the table, watch the video for help.