Create a graph that represents how a radioactive element will decay. % of original mass remaining 20 70 2 0 The graph below shows the breakdown of radon-222. What is the half-life of Rn-222? Le What fraction of the original sample will be left after 3 half-lives? Counts per minute 80 50 30 2 2 2 2 2 2 70 60 40 20 10 Time (Days) 10 6 CO How much of a 500g sample of potassium-42 is left after 37.2 hours if the half-life of potassium-42 is 124 hours. How much of a 100-gram sample of gold-198 is left after 8.10 days if its half life is 2.7 days? Half-Life 8 Time The table below shows the radioactive decay of a 600g sample of iodine-125 Mass (g) of Parent Isotope Half-lives (days) % of Parent Isotope Remaining Fraction of Parent Isotope Remaining 0 0 100% 1/1 600 60 1 50% 300 120 2 25% 150 180 3 12.5% 1/8 75 240 4 6.25% 1/16 37.5 300 5 3.125% 1/32 18.75 360 6 1.56% 1/64 9.4 practice a What percent of iodine is left after 5 half live have passed? b. What percent of iodine-125 has decayed if there are 37.5 grams of the original sample left? c. What is the half life of iodine-125? d. What mass of the iodine-125 has decayed after 6 half-lives? e. What fraction of the iodine-125 remains after 300 days have passed? f. How many half lives would have to pass for there to be only 12 grams remaining?