Question

Which isotope is appropriate for dating rocks that are billions of years old?

Answer 1

The answer would be uranium-238. I know it’s right cause I got a 100%.

Answer 2

Uranium-238.

Uranium - 238' s half lif time is 4.5 billion years. This isotope decays until the stable isotope Lead - 206.

It has been used to date the oldest rocks of the earth with a resulting age of approximately 4.0 billion years old.