A naturally occurring phosphorescent material, impure barium sulfate can glow in the dark for up to an hour after being exposed to sufficient sunlight.
Though carbon dating is extremely useful, it can only be used for things that formed about 60,000 years ago or earlier. That’s where La-Ba (lanthanum-barium) dating comes in. While barium-139 has a half-life of only 68 minutes, it decays into lanthanum-139, which has a half-life of around 100 billion years before it decays into barium-138, making it ideal for dating ancient granite.
Lanthanum has quite a few applications, the first of which was in gas lantern mantles as early as 1885. In modern times, lanthanum is used in some batteries, hydrogen sponges, mischmetal, electronic vacuum tubes, scintillators, special optical glasses, and occasionally in steel to improve its malleability and ductility.
As a metal, barium is used to remove unwanted gases from vacuum tubes (a process called gettering) and in various alloys, such as with nickel for spark plugs, alloyed with calcium, manganese, silicon, and aluminium as high-grade steel deoxidizers, or as an additive in steel and cast iron.
The compound barium sulfate is used as a drilling fluid in oil and gas wells, as well as a radiocontrast agent in X-ray imaging of the digestive system. Barium oxide coats the electrodes of fluorescent lamps, barium carbonate increases the refractive index of glass, and barium nitrate adds a green color to fireworks. Various other compounds are used as catalysts, superconductors, or as electroceramics.
As such a reactive metal, pure barium is rare and its health effects are not well studied. Water soluble compounds, however, are known to be poisonous and barium ions can cause serious health effects in the body. The element is not necessary for any known forms of life.
Carl Scheele was the first to determine that the mineral barite contained a new element in 1774 but he was unable to isolate the metal. It was only over thirty years later that Sir Humphry Davy managed to isolate pure barium in 1808 by electrolysis of barium salts. Davy was also the one to add the -ium ending, signifying a metallic element.
After demonstrating a reaction that sublimes a portion of iodine into its purple gas, Periodic Videos on YouTube discusses iodine’s reactivity, it’s occurrence in nature, and its necessity for human health.
Widely used in various medical applications, including as a disinfectant, iodine is also useful in analytical chemistry thanks to its reactions with various materials. It is commonly used in staining and turns dark blue in the presence of starch.
The heaviest essential element widely used by a variety of life forms, iodine is an essential trace element for life as we know it. Dietary iodine is frequently found in seafood, thanks to the elements presence in seawater, and a deficiency of it can lead to a variety of health problems. Such a deficiency is the leading cause of preventable intellectual disability and is the reason why salt is often iodized.
In its pure form, elemental iodine is toxic when ingested orally and can be lethal. However, it is often commonly used as a disinfectant in various forms.
Thanks to its radioactivity (in which it gives off intense alpha radiation), polonium is used as an atomic heat source to power radioisotope thermoelectric generators. Polonium is also occasionally alloyed with beryllium oxide as a neutron sources, as the BeO converts the alpha particles to neutrons. Finally, polonium has also been used in tools that eliminate static charges in items such as photographic plates and sheet plastic, though it has mostly been replaced by less dangerous materials.
Because of its intense radioactivity (polonium has no stable isotopes), this element is incredibly toxic and difficult to handle safely, even in small amounts. The median lethal dose is considered to be 4.5 Sv, which can be caused by ingesting as little as 50 nanograms or inhaling as few as 10 nanograms. Tobacco smoke from cigarettes also contains small amounts of polonium-210, contributing to many of cases of lung cancer.
Chromium is the twenty-fourth element on the periodic table, giving it twenty four protons and electrons. Though small amounts have been found naturally in rare minerals, most chromium is extracted from the ore chromite.
On the periodic table, the element is characterized as a transition metal. Given the sheer number of transition metals it is difficult to define any definite characteristics but, generally, transition metals are paramagnetic with more than one oxidation states. Also, metals typically (though not always) have high electrical conductivity as well as high density and high melting and boiling points.
Chromium is a hard and brittle steely-gray metal. It has high corrosion resistance and hardness as well as three stable isotopes.
