pure polonium-210 (k = 5.02 × 10−3 day−1) were used in a crime, based on radioactive disintegration alone, how long would it take for half the original isotope to disappear?     a. 2.9 years   b. 69.3 hours   c. 1.44 × 103 minutes   d. 210 years   e. 138 days

Sodium-24 has a half-life of 14.8 hours. How much of a 346.3 mg sodium-24 sample will remain after 3.7 days? mass remaining: mg

Macmillan l 30: F2 W S A 210.2 ng sample of an unknown radioactive substance was placed in storage and its mass measured periodically. After 47 days the amount of radioactive substance had decreased to 26.28 ng. How many half-lives of the unknown radioactive substance have occurred? number of half-lives: #3 H 80 F3 mmand E D A GA $ X C 4 OOD 886 F4 R F % от ото 5 V F5 T G ^ 6 B F6 Y & 7 H 8 F7 U N 00 * 8 DII FB J L - ( 9 M K DD F9 O . V - ... I 4 F11 { [ option + = ? 11 1 F12 } ] half-lives delete return st

Radioactive vanadium-48 decays with a half-life of 16.0 days. a. What is the value of k in s? k = b. A sample contains 84.0 mg *°V. How many decay events will be produced in the first second? Assume the atomic mass of **V is 48.0 u. decays/s c. A chemist obtains a fresh sample of 48 V and measures its radioactivity. She then determines that to do an experiment, the radioactivity cannot fall below 25% of the initial measured value. How long does she have to do the experiment? days

Cancer therapy with radioactive rhenium-188 shows promise in patients suffering from colorectal cancer. a. Write the symbol for rhenium-188 and determine the number of neutrons, protons, and electrons. b. The half-life of rhenium-188 is 17 hours. If it takes 30 minutes to bind the isotope to an antibodythat delivers the rhenium to the tumor, what percentage of the rhenium remains after binding tothe antibody?

One of the radioactive isotopes used in chemical and medical research is iodine- 125, which has a half-life of 61 days. How long would it take for 0.25 g to remain of a 1.00 g sample of iodine-125? A) 244 days B) 122 days C) 61 days D) 31 days

2. Tellurium-123 is a radioactive isotope occurring in natural tellurium. The decay constant is 1.7 x 1021 / s. What is the half-life in years?