|A single atom of barium has 56 protons in its nucelus and in its
elemental form has 56 electrons in electron orbitals surrounding the
nucelus. Most naturally ocurring barium atoms have 82 neutrons in their
nucleus, but there are seven stable isotopes (different numbers of
neutrons), naturally occuring.
Pure barium is metallic and shares electrons with other barium atoms in the metal, allowing electrical conduction. Barium also forms ionic compounds by donating two electrons to the other atoms in the molecules it forms. Most of these ionic compounds are soluble in water, and all barium compounds that dissolve in water or acids are poisonous.
A barium nucleus is very heavy, with the large numbers of protons and neutrons it has, and it absorbs X-rays very well. Barium sulfate (BaS04) is used medically as a "radiotracer" -- it has a low solubility in water so it does not harm the patient, and it absorbs X-rays wherever it goes, so it makes shadows on X-ray film, illuminating blood vessels and digestive organs.
The name "barium" comes from the greek word for "heavy", and was given this name because it is a very dense element.
Jason (and Tom)
(republished on 07/19/06)