Halogens - Chlorine, Bromine, Iodine, Astatine, Fluorine, Unexplored Sources And Problems
elements chemical compounds exist
The halogens are a group of chemical elements that includes fluorine, chlorine, bromine, iodine, and astatine. Halogen comes from Greek terms meaning "produce sea salt." None of the halogens occur naturally in the form of elements, but, except for astatine, they are very widespread and abundant in chemical compounds where they are combined with other elements. Sodium chloride, common table salt, is the most widely known.
All of the halogens exist as diatomic molecules when pure elements. Fluorine and chlorine are gases. Bromine is one of only two liquid elements, and iodine is a solid. Astatine atoms exist only for a short time and then decay radioactively. Fluorine is the most reactive of all known elements. Chemical activity, the tendency to form chemical compounds, decreases with atomic number, from fluorine through iodine. Simple compounds of these elements are called halides. When one of the elements becomes part of a compound its name is changed to an -ide ending, e.g., chloride.
Additional Topics
Chlorine was the first halogen to be separated and recognized as an element. It was named in 1811 by Humphry Davy from a Greek term for its greenish yellow color. Huge deposits of solid salt, mostly sodium chloride, and salts dissolved in the oceans are vast reservoirs of chloride compounds. "Salt" is a general term for a metal and nonmetal combination; there are many different salts…
The next heaviest element in the halogen family is bromine, named from a Greek word for stink, because of its strong and disagreeable odor. It was first isolated as an element in 1826. Bromine is a reddish brown liquid that vaporizes easily. The vapors are irritating to the eyes and throat. Elemental bromine is made by oxidation, removal of electrons from bromide ions in brine. Brines in Arkansas …
The heaviest stable halogen is iodine. Iodine forms dark purple crystals, confirming its name, Greek for violet colored. It was first obtained in 1811 from the ashes of seaweed. Iodine is purified by heating the solid, which sublimes, or goes directly to the gas state. The pure solid is obtained by cooling the vapors. The vapors are irritating to eyes and mucous membranes. Iodine was obtained comm…
Astatine could be described as the most rare element on Earth. All isotopes, atoms with the same number of protons in the nucleus and different numbers of neutrons, are radioactive; even its name is Greek for "unstable." When an atom decays its nucleus breaks into smaller atoms, subatomic particles, and energy. Astatine occurs naturally as one of the atoms produced when the uranium 2…
Fluorine was the most difficult halogen to isolate because it is so chemically reactive. H. Moissan first isolated elemental fluorine in 1886, more than seventy years after the first attempts. Moissan received the 1906 Nobel Prize for Chemistry for this work. The technique that he developed, electrolysis of potassium fluoride in anhydrous liquid hydrogen fluoride, is still used today, with some mo…
Most of the organic halogen compounds mentioned are made synthetically. However, there are also natural sources. In 1968 there were 30 known naturally occurring compounds. By 1994 around 2,000 had been discovered, and many biological organisms, especially marine species, those in the oceans, had not been looked at as yet. Halogenated compounds were found in ocean water, in marine algae, in corals,…
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User Comments
almost 5 years ago
Astatine is my element for a science project.
6 months ago
Very informative! Easy to understand!