Radium components: compounds of barium, which gave a brilliant green flame color, and unknown radioactive compounds which gave carmine spectral lines that had never been documented before. The Curies found the radioactive compounds to be very similar to the barium compounds, except that they were more insoluble. This made it possible for the Curies to separate out the radioactive compounds and discover a new element in them. The Curies announced their discovery to the French Academy of Sciences on 26 December 1898. The naming of radium dates to about 1899, from the French word "radium", formed in Modern Latin from "radius"
Polonium and sources of neutrons and alpha particles. This radioactivity makes polonium dangerously toxic. Po is an alpha emitter that has a half-life of 138.4 days; it decays directly to its stable daughter isotope, Pb. A milligram (5 curies) of Po emits about as many alpha particles per second as 5 grams of Ra. A few curies (1 curie equals 37 gigabecquerels, 1 Ci = 37 GBq) of Po emit a blue glow which is caused by ionisation of the surrounding air. About one in 100,000 alpha emissions causes an excitation in the nucleus which then results in the emission of