In the fall of 2002, a group of scientists at Los Alamos National Laboratory determined that the critical mass of neptunium-237 is about 60.0kg. The critical mass of a fissionable material is the minimum amount that must be brought together to start a chain reaction. Neptunium-237 has a density of 19.5g/cm3. What would be the radius rr of a sphere of neptunium-237 that has a critical mass?

A 21186Rn nucleus undergoes alpha decay according to the reaction 21186Rn → 20784Po + 42He. Determine the following. (Let the atomic mass of 21186Rn be 210.9906 u, the atomic mass of 20784Po be 206.9816 u and the atomic mass of 42He be 4.0026 u.)   (a)Q value (in MeV) for the process (Enter your answer to at least two decimal places.)   (b)Kinetic energy (in MeV) of the alpha particle after the decay (Enter your answer to at least two decimal places.)   (c) Kinetic energy (in MeV) of the daughter nucleus after the decay

A scientist is studying a 2.234 g sample of thorium-229 (t1/2 = 7340 yrs) in a laboratory.    (a) What is its activity in Bq?   Answer: x 10^ Bq   (b) What is its activity in Ci?   Answer: x 10^ Ci

The mass defect for potassium-40 is: -___x10-28kg. (Give your answer with 3 sig digs and do not include units) Use mass of proton = 1.007276 u mass of neutron = 1.008665 u actual mass = 39.9687 u

How many half-lives must elapse until (a) 77% and (b) 99 % of a radioactive sample of atoms has decayed? Part A Express your answer using two significant figures. ΜΕ ΑΣΦ Submit Request Answer Part B Express your answer using two significant figures. ΕΕ ΑΣΦ ? ?

Experimentally, it is found that natural potassium emits 31 beta particles per second per gram and 3.4 gamma rays per second per gram. With this data, determine the half- life period of K40. (The isotopic concentration of K40 is 0.0118% .)

One method for determining the age of ancient objects is by radiocarbon dating. Natural processes convert nitrogen to Carbon-14, a radioactive isotope with a half-life of 5730 years. When they are alive, animals assimilate Carbon-14 through the food chain. When an animal dies, it stops replacing its carbon and the amount of Carbon-14 decays exponentially. (a) Suppose the minimum detectable amount is 0.1% of the initial amount. What is the maximum age of a fossil that we could date using Carbon-14? (b) Suppose we wanted to date a fossil that was potentially 70 million years old. A radioactive isotope with what half-life would be required?

A group of geochemists have been analyzing a sample of radioactive material. After plotting ln(a) versus t, they calculate a slope value of -1.00·10−9 s−1. Determine the half-life of this material in years.

Please help me answer the following.

The radionuclide 32P (T1/2 = 14.28 d) is often used as a tracer to follow the course of biochemical reactions involving phosphorus. (a) If the counting rate in a particular experimental setup is initially 3050 counts/s, how much time will the rate take to fall to 170 counts/s? (b) A solution containing 32P is fed to the root system of an experimental tomato plant, and the 32P activity in a leaf is measured 3.48 days later. By what factor must this reading be multiplied to correct for the decay that has occurred since the experiment began?