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This is a list of radioactive nuclides (sometimes also called isotopes), ordered by half-life from shortest to longest, in seconds, minutes, hours, days and years. Current methods make it difficult to measure half-lives between approximately 10 −19 and 10 −10 seconds.
In this situation it is generally uncommon to talk about half-life in the first place, but sometimes people will describe the decay in terms of its "first half-life", "second half-life", etc., where the first half-life is defined as the time required for decay from the initial value to 50%, the second half-life is from 50% to 25%, and so on.
Mercury (as methylmercury) in the body has a half-life of about 65 days. Lead in the blood has a half life of 28–36 days. [29] [30] Lead in bone has a biological half-life of about ten years. Cadmium in bone has a biological half-life of about 30 years. Plutonium in bone has a biological half-life of about 100 years.
All other isotopes have half-lives shorter than one hour, except for 231 U (half-life 4.2 days) and 240 U (half-life 14.1 hours). [7] The shortest-lived known isotope is 221 U, with a half-life of 660 nanoseconds, and it is expected that the hitherto unknown 220 U has an even shorter half-life. [ 122 ]
First, neptunium-238 (half-life 2.1 days) was synthesized, which then beta-decayed to form the new element with atomic number 94 and atomic weight 238 (half-life 88 years). Since uranium had been named after the planet Uranus and neptunium after the planet Neptune , element 94 was named after Pluto , which at the time was also considered a planet.
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Hamm might be able to come back eventually and participate in a shortened version of the program, Greenwell said. But there was a three-month waiting list. Greenwell said, half joking, that he wanted to make T-shirts that read, “One in 10 make it. Are you the One?” In late September, Hamm was transferred back to Grateful Life for another try.
Plutonium-244 is the most stable isotope of plutonium, with a half-life of about 80 million years. It is not significantly produced in nuclear reactors because 243 Pu has a short half-life, but some is produced in nuclear explosions. 244 Pu has been found in interstellar space [13] and has the second longest half-life of any non-primordial ...