Uranium isotope relative abundance at diff times

AI Thread Summary
The discussion focuses on determining the relative abundance of uranium isotopes at the time of Earth's formation, approximately 4.6 billion years ago. Current abundances are given as 99.2745% for 238U, 0.7196% for 235U, and 0.0055% for 234U. Participants suggest using the half-lives of these isotopes to calculate their past abundances by applying decay equations. It is noted that all isotopes decay to Thorium, which may aid in reversing the decay process to estimate initial amounts. The conversation emphasizes the need for a clear approach to this calculation.
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Homework Statement



The relative abundance of uranium isotopes in today’s Earth crustal material is:
99.2745% 238U
0.7196% 235U
0.0055% 234U
What were the relative abundances when the Earth was formed 4.6x109 years ago?


Homework Equations



t = age = 1/lambda * ln(N/No)

N = No*e^lambda*t

The Attempt at a Solution



i don't know how to approch this...
 
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What are the half-lives of the 3 isotopes?

Since they all decay to Thorium then maybe if you work them backwards you can turn back the clock to see what was around 4 and a half billion years ago?
 
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