Dating Radioactive Decay
Radioactive dating ?
It has been shown that the half-life for this radioactive isotope is 20 years. In the year 2000, an archaeology team unearths pottery and is using this isotope for radiometric dating to place the age of the pottery. It is shown that 95% of the nuclei have decayed.
How long ago was the pottery made?
please explain how to get the answer… thanks!! i dont want to come across a question like this on a test and not know how to solve it without help..
the relevant equations (first order kinetics) are
ln(Nt/N0) = -kt
and
t1/2 = 0.693/k
now if t1/2 is 20 yr
k = 0.693/20 = 0.03465
95% decay means that 5% nuclei have not decayed. So Nt/N0 = 0.05 (Nt is the number of nuclei left at time t)
therefore
ln 0.05 = -0.03465t
solve for t in years. It gives t = 86.5 years ago
Chemistry: Radioactive Decay and Half-Life (Carbon Dating)
