Uranium-235 has a half-life of 713 million years. Would uranium-235 or carbon-14 be more useful for dating a fossil from Precambrian Time? Explain.

Answer: Uranium-235.

Radioactive isotopes are used to determine the age of antique objects, including fossils.

The half-life time of the radioactive elements is what permits the process of dating.

The half-life of C-14 is too short to be useful to date too old objects.

Precambrian time is the most antique era. C-14 hal-life is about 5730 years and Precambrian time is millions or billions of years ago. Given that the hal-life of U-235 is 704 million years it is appropiate to date the fossils from the Precambrian era.