Brief Description:
Radium is a metallic white when fresh, but oxidation turns the substance black rapidly. Radium decomposes in water, exhibits light, and turns flames red when burned. The first radioactive substance discovered, radium also phosphoresces in certain salts. At the turn of the century, it was used to illuminate watch dials, until found to be radioactively toxic. It is thought that radiation poisoning from radium killed Marie Curie.