Hi I have one important question n homework.
Which radioactive isotope is better to date a fossil 20000 years old,6 billion years old and 20 billion years old?please help me a.s.a.p:confused:

Your help is really appreciated.thank youu
Xx

I'm not going to research it for you, but obviously you want a radioactive isotope that has a half life close to the number of years you're trying to measure. That way, approximately half of the material will be the original element and half will be the decomposed element. That makes measuring the concentrations of the elements the most accurate.