Isotopes of radium
Radium (Ra) has no stable or nearly stable isotopes, and thus a standard atomic weight cannot be given. The longest lived, and most common, isotope of radium is Ra with a half-life of . Ra occurs in the decay chain of U (often referred to as the radium series). Radium has 33 known isotopes from Ra to Ra. In 2013 it was discovered that the nucleus of radium-224 is pear-shaped. This was the first discovery of an asymmetric nucleus.