Calculate the time required for 21.80 % of a sample of 190X (t1/2 = 460.0 h) to decay. Use the formula with 0.693 instead of ln 2.

The radioactive isotope 212pb has a half-life of 10.64 h. A sample containing this isotope has an initial activity (t = 0) of 55.0 pCi. Calculate the number of nuclei that decay in tl time interval between t, = 7.0 h and t, = 15.0 h. nuclei

Balance the following nuclear reactions

How long does it take a 30.0 mCimCi sample of gold-198 to decay so that only 7.50 mCimCi remains?

Even though plutonium−239 (t1/2 = 2.41 × 104 yr) is one of the main fission fuels, it is still a radiation hazard present in spent uranium fuel from nuclear power plants. How many years does it take for 94% of the plutonium−239 in spent fuel to decay?

Strontium-90 is one of the most hazardous products of atomic weapons testing because of its long half-life (t1/2 = 28.1 years) and its tendency to accumulate in bone.(a) Write nuclear equations for the decay of 90Sr via the successive                   emission of two electrons (beta particles).(b) The atomic mass of 90Sr is 89.9073 u and that of 90Zr is 89.9043 u.               Calculate the energy released per 90Sr atom, in MeV, in decaying to  90Zr.(c) What will be the initial activity of 1.00 g of 90Sr released into the                    environment, in disintegrations per second?(d) What activity will the material from part (c) show after 100 years?

Radium-223 has a half-life of 11.4 days.Approximately how long would it take for the activity of a sample of 223Ra223Ra to decrease to 1.50 %% of its initial value? Express your answer with the appropriate units.

Fluorine-18 is a radioactive isotope use in a variety of medical imaging proceduresincluding positron emission tomography (PET) scans. Fluorine-18 decays by positron emissionwith a half-life of 1.83 hours. A medical sample containing 18F has an activity of 4.00 millicuries. How many picograms of18F are present in the sample? The atomic mass of 18F is 18.00 g/mol. (1 picogram = 1×10–12g 1 Curie = 3.7×10–10 decays/sec 1 millicurie = 1×10–3 Curies)