Measurements indicate that 27.83% of all rubidium atoms currently on the earth are the radioactive 87Rb isotope. The rest are the stable 85Rb isotope. The half-life of 87Rb is 4.75 * 1010 y. Assuming that no rubidium atoms have been formed since, what percentage of rubidium atoms were 87Rb when our solar system was formed 4.6 * 109 y ago?

If we start with 6.4*10^12 atoms of a radioactive material with a half life of 1.2 days, how many atoms remain after 6 days?

Radioactive decay is always a first-order kinetic process. Uranium-238 decays to lead-206,which is stable, with an effective half-life of 4.51 billion years. Sediment from the oceancontains 0.00150 grams uranium-238 and 4.60 x 10-4 grams lead-206. Assume lead-206 isformed only by uranium-238 decay, and there was no lead-206 present when the sedimentformed; estimate the age of the sediment.

What is the binding energy per nucleon for the following isotopes? Suppose that mn = 1.008665 u, m1H =1.007825 u, 1u= 931.494 MeV/c2. 1) What is the binding energy per nucleon for 90Sr? (Express your answer to six significant figures.) 2) What is the binding energy per nucleon for 129I? (Express your answer to six significant figures.) 3) What is the binding energy per nucleon for235U? (Express your answer to six significant figures.) 4) What is the binding energy per nucleon for 56Fe? (Express your answer to six significant figures.)

How long would it take half of the atoms of 146C to decay into 147N? The half-life of 146C is 5,730 years.