the most common isotope of uranium found in nature, with a relative abundance of 99%

a very rare radioactive isotope; before Marie Curie's discovery of polonium in 1898, uranium and thorium were the only known radioactive elements

a chemical element with the symbol I and atomic number 53

an unstable isotope of lead that decays by emitting radiation

the isotope of bismuth with the longest known half-life of any radioisotope that undergoes α-decay