Question

1. We start with 400 atoms of Uranium-238. How many remain after 4.5 billion years? _______ After 9 billion years? _______ After 13.5 billion years? ________

2 . How long will it take for ½ of the original amount of Rubidium-87 to decay? _______

3. Carbon-14 has a half-life of 5,730 years. How does that compare to those listed in the chart?


What possible advantages or disadvantages would this give C-14 when used for radiometric dating?

Answer 1

The half life of Uranium-238 is 4.5 billion years, thus:
After 4.5 billion years: 200 atoms
After 9 billion years: 100 atoms
After 13.5 billion years: 50 atoms

The time taken will be equal to its half-life, which is 48.8 billion years

The half life is far less than those of the substances in the chart. This allows Carbon-14 to be used to determine the age of younger substances, such as artifacts and fossils.