What is the half life of uranium?

== == Naturally occurring uranium is a mixture of three isotopes. The most abundant (greater than 99%) and most stable is uranium-238 (half-life 4.5 x 109 years); also present are uranium-235 (half-life 7 x 108 years) and uranium-234 (half-life 2.5 x 105 years). Different isotopes have different half-lives. The most stable isotope of uranium, 238U, has a half-life of about 4.5 billion years.