Introduction
What are Chalcogenides?
The chalcogens are the elements in group 16 of the periodic table, just as group 17 are the halogens.
Chalcogenides are compounds that contain at least one chalcogen element, but when talking about chalcogenides in general we usually exclude the oxides (O) (as they are far more common and are really their own special class of compounds), the polonides (Po) and the synthetic element ununhexium (Uuh) (as as they are radioactive, rare and/or short lived). This means that we're really talking about the sulphides (S), selenides (Se) and tellurides (Te).
Where Does The Name Chalcogenide Come From?
During The 1930's a research group at the Institute of Inorganic Chemistry, University of Hannover, Germany, were studying the relationship between the physical properties of groups of elements and their position in the periodic table. In their daily discussions it became useful to refer to certain groups of elements by characteristic names such the alkalis, the halogens, etc. However, the group of the elements in group six of the periodic table, O, S, Se, and Te lacked such a name.
In about 1932, one of the members of the research group suggested calling these elements the "chalcogens" ("ore formers" from chalcos, the old Greek word for "ore" and -gen the word for "formation" ) and their compounds "chalcogenides" .
These names quickly became popular and were soon used regularly in publications by members of the group and also by other researchers studying these elements because they were analogous to the well-known terms "halogens" ("salt formers"), and "halogenides" for the neighboring elements in the periodic table, the majority of halogenides being salts and chalcogenides being ores.
Heinrich Remy, the author of a comprehensive text book on inorganic chemistry at the time, also supported the new term and when he became the German member of the Committee of the International Union of Chemistry for the Reform of the Nomenclature of Inorganic Chemistry (later IUPAC), he recommended that "the elements oxygen, sulfur, selenium and tellurium may be called chalcogens and their compounds chalcogenides". This idea was accepted and within just a few years the term was used worldwide, particularly in textbooks.
Reference: http://jchemed.chem.wisc.edu/Journal/Issues/2001/Oct/abs1333_1.html
What Properties Do Chalcogen Elements Possess?
Chalcogenides are commonly found as minerals in the ground.
Oxygen and sulfur are nonmetals, and polonium, selenium and tellurium are metalloid semiconductors (i.e. their electrical properties are between those of a metal and an insulator). Nevertheless, tellurium, as well as selenium, is often referred to as a metal when in elemental form.
The formal oxidation number of a chalcogen is generally -2 in a chalcogenide but other values (e.g. -1 in pyrite [FeS2]) can be attained.
The highest formal oxidation number +6 is found in sulfates, selenates and tellurates, e.g. in Na2SeO4 (sodium selenate).
Random Chalcogenide Facts:
Chalcogenides are responsible for the well known iron ore called pyrite, FeS2 aka. Fool's Gold
In Colorado, USA there is a town called Telluride; The town got its name due to a gold rush when AuTe2 was discovered there