Radium is an intensely radioactive alkaline earth metal discovered by Marie and Pierre Curie.
Core Principles & Analysis
Marie and Pierre Curie announced radium in December 1898 after finding it in pitchblende; isolating a decigram of pure radium chloride took Marie nearly four more years of processing tonnes of ore residue.
Radium-226, part of the uranium-238 decay chain, has a 1,600-year half-life; its use in glow-in-the-dark watch-dial paint caused the infamous radiation poisoning of the 'Radium Girls'.
Radium returned to medicine in 2013 when radium-223 dichloride was approved for prostate cancer that has spread to bone, exploiting radium's calcium-like bone-seeking chemistry.