It won't help the geologist one iota.
Half-lives of certain elements called radioisotopes can be used to calculate the date of crystallization of igneous rocks, and only igneous rocks. In other words, the age of igneous rocks can be determined. The process is called radiometric age dating, and it will not work on sedimentary rocks.
Fossils are not found in igneous rocks - only sedimentary rocks. Therefore knowing the half-life of an element will not help to establish the age of a fossil, except perhaps indirectly if there is a layer of volcanic ash in close proximity to the fossil bearing strata, or if there is a series of igneous dikes bracketing the fossil bearing strata.
It is a common myth that radiometric age dating can be used to date fossils.
This looks like a homework question written by someone who doesn't know much about geology, fossils, or age dating. If this question represents the type of talent teaching earth sciences, then I am fearful of the future of my profession.