

Study with the several resources on Docsity
Earn points by helping other students or get them with a premium plan
Prepare for your exams
Study with the several resources on Docsity
Earn points to download
Earn points by helping other students or get them with a premium plan
Community
Ask the community for help and clear up your study doubts
Discover the best universities in your country according to Docsity users
Free resources
Download our free guides on studying techniques, anxiety management strategies, and thesis advice from Docsity tutors
halflife of radioactive elements definiton and formula
Typology: Study notes
1 / 2
This page cannot be seen from the preview
Don't miss anything!
Half life of radioisotopes Half-life , in radioactivity, the interval of time required for one-half of the atomic nuclei of a radioactive sample to decay or, equivalently, the time interval required for the number of disintegrations per second of a radioactive material to decrease by one-half. Let N be the size of the population of the radioactive atoms at a given time t, dN be the amount by which it decreases in time dt. The rate of change is given as dN/dt = - λN, where λ is the decay constant. N = N 0 e-λt N0 = Initial number of radioactive atoms at t = 0 the population decays exponentially at a rate that depends on decay constant. The time taken for half of the radioactive atoms to decay is called the half-life. N = N 0 e-^ λt if T is the half life then, T = t N = N0/ 2 Substituting we get, N0/2 = N 0 e-^ λt ½ = e-^ λt 2 = e λt Loge 2 = λ T 0r T= 0.693/ λ The half life of a radioactive element is inversely proportional to the decay constant of that element.
Half life value of some important radioisotopes, Americium- 241 432.2 years Lutetium- 177 6.71 days Barium- 133 10.74 years Molybdenum- 99 66 hours Calcium- 45 163 days Phosphorus- 32 14.29 days Phosphorus- 33 25.4 days Cadmium- 109 464 days Carbon- 14 5730 years Plutonium- 239 24,065 years Cesium- 137 30 years Polonium- 210 138.38 days Cobalt- 60 5.271 years Selenium- 75 119.8 days Hydrogen- 3 12.35 years Indium- 111 2.83 days Technetium- 99 213,000 years Technetium- 99m 6.02 hours Iodine- 131 8.04 days Xenon- 127 3 6.41 days Iodine- 129 15,700,000 years Iodine- 125 60.14 days Uranium- 238 4,468,000,000 years Uranium- 235 703,800,000 years