Radium

The Simple English Wiktionary has a definition for: radium.

Radium is a chemical element. The symbol for radium is Ra, and its atomic number is 88. It was discovered by Marie Curie and Pierre Curie in the form of radium chloride in 1898. It is a slivery-white alkaline earth metal, but it turns black quickly when it is exposed to nitrogen in the air. All isotopes of radium are radioactive. The radioactivity of radium causes it to glow in the dark.

Radium is used in many things, such as glowing watches, which are now banned because they can cause radiation poisoning. Some of the things radium was used for are now made using less dangerous radioactive elements, such as promethium. It can be used in treating cancer.^[1]

In nature, radium is found in tiny amounts in uranium and thorium ores. It does not exist naturally inside of people or other living things; it is dangerous when taken in because it takes the same place as calcium.

1. ↑ "Radium 223 (Xofigo) | Cancer treatment | Cancer Research UK". www.cancerresearchuk.org. Retrieved 2021-06-08.