Both ²³⁸U and ²³²Th decay to stable isotopes of lead. ²²²Rn (t_1/2 = 3.8 d) is an intermediate nuclide in the ²³⁸U series. ²¹⁸Rn (t_1/2 = 56 s) is an intermediate in the ²³²Th decay series. In which series would diffusion of gaseous radon cause the greater error in the computed age of a rock (see Exercise 14.35)?

Data from exercise 14.35

The ²³⁸U series can be used to date minerals containing uranium by measuring the ratio of ²³⁸U to ²⁰⁶Pb, but all of the decay products have to remain in the mineral through several of their half-lives so that essentially all the ²³⁸U that decays become ²⁰⁶Pb. One of the decay products in this series is the noble gas, ²²²Rn. How would the experimentally determined age of the mineral be affected if some of the radon diffused from the rock?