Atomic number: 56
Symbol: Ba
Category: alkali earth metal

Density at 25°C: solid: density: 3.51 g·cm−3

Barium is perhaps most known in the medicine as a contrast agent (in the form of barium sulphate and water) for x-rays to show activity in the digestive tract. But barium compounds are used in fireworks to produce a green colour. 

Barium held under argon gas. image: adapted from wikipedia

Curiosity: the symbol Ba is used as part of the art work title for the TV Drama Breaking Bad.

Use, natural applications or common combinations: 

  • drilling fluid
  •  removes unwanted gases (gettering) from vacuum tubes
  • some alloys

Basic characteristics:

  • Standard atomic weight: 137.327(7)
  • Melting point:  727 °C
  • Boiling point: 1897 °C
  • Radioactivity: mostly naturally stable, possibly some isotopes are radioactive but very long half-lives.