Atomic number: 88

Symbol: Ra

Category: Alkali earth metal

Density at 25°C: solid: density: 5.5 g·cm−3

Radium occurs in nature as part of uraninite ores but only in very trace quantities. It is most well know as being discovered by Marie Skłodowska-Curie and Pierre Curie in 1898.  It was historically important in the scientific study of radioactivity and developing technologies for using radiation. 

Sample of copper coated with a layer of radium, covered with protective coating. image: adapted from wikipedia

Use, natural applications or common combinations: 

  • historically for fluorescent paints
  • historically used to discover the structure of the atom by Rutherford.

Basic characteristics:

  • Standard atomic weight: (226)
  • Melting point: 700 °C
  • Boiling point: 1737 °C
  • Radioactivity: all radioactive
  • 223Ra, 224Ra, 226Ra and 228Ra are all generated naturally in the decay of either uranium or thorium.  226Ra is the most stable with half life of 1601 years via alpha decay.