Radon (86Rn222) is an unstable isotope that undergoes α decay with a half-life of3.8 days.(i) Identify the daughter nucleus in this decay process. Show how you obtained youranswer. [2 marks](ii) Calculate the activity of a sample containing 2.0 x 108 atoms of 86Rn222.[3 marks](iii) Estimate how many α particles are emitted in the first hour after the sample isformed.
Question
Radon (86Rn222) is an unstable isotope that undergoes α decay with a half-life of3.8 days.(i) Identify the daughter nucleus in this decay process. Show how you obtained youranswer. 2 marks Calculate the activity of a sample containing 2.0 x 108 atoms of 86Rn222.3 marks Estimate how many α particles are emitted in the first hour after the sample isformed.
Solution
(i) In alpha decay, a nucleus emits an alpha particle, which is a helium nucleus (2 protons and 2 neutrons). Therefore, the atomic number decreases by 2 and the mass number decreases by 4. For Radon (86Rn222), the daughter nucleus would be Polonium (84Po218). Here's the equation:
86Rn222 → 84Po218 + 2He4
(ii) The activity of a radioactive sample is given by the equation A = λN, where λ is the decay constant and N is the number of atoms. The decay constant can be found using the equation λ = ln(2) / T, where T is the half-life.
First, convert the half-life to seconds: 3.8 days = 3.8 * 24 * 60 * 60 = 328320 seconds.
Then, calculate the decay constant: λ = ln(2) / 328320 = 2.11 x 10^-6 s^-1.
Finally, calculate the activity: A = λN = 2.11 x 10^-6 s^-1 * 2.0 x 10^8 atoms = 422 Bq.
(iii) The number of alpha particles emitted in a given time is given by the equation N = N0 * (1 - e^-λt), where N0 is the initial number of atoms, λ is the decay constant, and t is the time.
First, convert the time to seconds: 1 hour = 60 * 60 = 3600 seconds.
Then, calculate the number of alpha particles: N = 2.0 x 10^8 atoms * (1 - e^-2.11 x 10^-6 s^-1 * 3600 s) ≈ 2.7 x 10^6 alpha particles.
Similar Questions
Radon-210 (21086Rn) decays by alpha decay to an isotope of polonium (Po) with a mass number of .
Radon (Rn) decays in a first-order process with a half-life of 3.823 days. What is thevalue of the rate constant in days -1 ?
The half-life of this americium nuclide is 470 years. A sample of this nuclide contains 8.0x10^14 atoms. After some time, 6 * 10 ^ 14 americium atoms have decayed.Calculate the time required for this decay
Radium-226 is radioactive and has a half life of 1600. years. How much of a 9.70mg sample would be left after ×6.01103 years?Round your answer to 2 significant digits. Also, be sure your answer has a unit symbol.
Derive an expression that relates the half-life and the decay constant for a sample of aparticular radioactive nucleus. Calculate the half-life and decay constant for a radioactiveisotope sample if the initial number of radioactive atoms is 450 and this reduces to 63 after24.3 hours.
Upgrade your grade with Knowee
Get personalized homework help. Review tough concepts in more detail, or go deeper into your topic by exploring other relevant questions.