All practice pages/Interatomic theory/Elements
Element 56, an alkaline earth metal
Heavy by name and poisonous as a soluble salt, yet swallowed safely as a white paste so doctors can X-ray the gut.
Period 6, group 2. The other alkaline earth metals are tinted, and every cell opens its own article.
Barium has 56 electrons, one for every proton, so the atom carries no charge. Below are the same 56 electrons written two ways.
1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 5s² 5p⁶ 6s²
Short form: [Xe] 6s², where [Xe] stands for the 54 electrons xenon already has.
The simple form counts electrons shell by shell. The orbital form says which subshell each one sits in: s holds 2, p holds 6, d holds 10 and f holds 14. Shell 3 here is 3s² 3p⁶ 3d¹⁰, and 2 + 6 + 10 is 18.
Barium sits in period 6 and has 6 shells. The period number counts the shells.
The outer shell holds 2 electrons. Those are the ones barium can lose, gain or share, so they are the ones that decide what it bonds with. For a main-group element the group number gives that count: group 2 means 2.
Two valence electrons, which barium gives up to form the Ba²⁺ ion in its compounds.
Mined mostly as barite (BaSO₄), in China, India and Morocco, and as witherite (BaCO₃).
Carl Wilhelm Scheele identified baryta, barium oxide, as a new earth in 1774, and Humphry Davy isolated the metal in 1808 by electrolysis. The name comes from the Greek barys, heavy, after the dense mineral barite.
Most barite is ground up for drilling mud, where its weight keeps oil and gas wells under control. Barium sulfate, which does not dissolve, is swallowed or given as an enema so the digestive tract shows up on X-rays. Barium compounds also make green fireworks, and barium goes into glass, ceramics and spark plugs.
Barium compounds that dissolve in water, such as barium chloride and barium carbonate, are poisonous. Barium sulfate is safe for X-rays only because it does not dissolve.