Uranium
Uranium-238 is the most stable isotope of uranium, with a half-life of about 4.468 years, roughly the age of the Earth. Uranium-235 has a half-life of about 7.13 years, and uranium-234 has a half-life of about 2.48 years.
For natural uranium, about 49% of its alpha rays are emitted by each of U atom, and also 49% by U (since the latter is formed from the former) and about 2.0% of them by the U. When the Earth was young, probably about one-fifth of its uranium was uranium-235, but the percentage of U was probably much lower than this.
Einsteinium
Nineteen nuclides and three nuclear isomers are known for einsteinium with atomic weights ranging from 240 to 258. All are radioactive and the most stable nuclide, Es, has a half-life of 471.7 days. Next most stable isotopes are Es (half-life 275.7 days), Es (39.8 days) and Es (20.47 days). All of the remaining isotopes have half-lives shorter than 40 hours, and most of them decay within less than 30 minutes. Of the three nuclear isomers, the most stable is Es with half-life of 39.3 hours.