5. Co-60 has a half life of 5.3 years. If a pellet that has been in storage for 26.5 years contains 14.5g of Co-60, how much of this radioisotope was present when the pellet was put in storage?

Uranium-lead (U-Pb) dating of geological samples is one of the oldest and most refined radiometric dating methods, able to determine ages of about 1 million years to over 4.5 billion years with precision in the 0.1–1% range. The U-Pb dating method relies on two separate decay chains, one of which is the actinium series from 235U to 207Pb, with a half-life of 704 million years.   Geologists unearth a sample of zircon that appears to be a closed system. They find 0.714  grams of 207Pb for 1.000 grams of 235U present. Approximately how old is the sample? _______ yrs

If tritium has a half life of 12.26 years, how old is a sample if two-thirds of it is now the daughter isotope? What type of decay is responsible if the daughter is Helium-3?

6.  If Nitrogen-14 absorbs an alpha particle and then emits a Hydrogen-1, what is the resulting nucleus? 7.  If Au-185 emits an alpha particle, what is the nucleus formed? 8.  What nucleus emits an alpha particle and forms Th-234?

Explain how "carbon dating" is used to establish the age of once living things.

Modern household smoke detectors contain a tiny speck of the element Americium (Am, atomic number 95, atomic mass 241), which has a half-life of 432 years and an activity of (roughly) of 37,000 decays per second. a) What is the approximate mass of this speck? (Hint: the atomic mass of this isotope is approximately 241.06 u). b) This isotope is an alpha emitter. Is its radiation likely to be a hazard to the household members while the smoke detector is on the ceiling? Explain.

If 232Th (half-life 1.4 × 1010 years) and 238U (half-life 4.5 × 109years) werepresent in equal amounts when the earth was formed, calculate their relative abundance atpresent. Note: The age of the earth is 4.54 billion years. NTh(t)/NU(t)= ?

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.

The activity of a particular radioactive nuclide falls from 1 × 1011 Bq to 2 × 1010 Bq in 10 hours. Calculate the half life of the nuclide.

Assume you found a radioactive isotope that has a 1 million year half-life in an "old" bone. If you were to measure a 20% "parent" to 80% "daughter" ratio, how old is the bone? How would a bone twice as big change the count rate and the half-life?