From left to right: gray and red selenium
T
The
crystal structure of hexagonal -tellurium
P
-Po
cubic allotrope
structure
History Of Discovery
Sulfur (S). Among the elements of group VI, except oxygen, еру most remarkable is sulfur. Elemental sulfur is met in nature in large beds, therefore sulfur has been known since ancient times and is already mentioned in works of Homer. In the works of alchemists sulfur takes a large part, since it was considered to expresse one of the fundamental properties of nature - combustibility.
Since long ago sulfur was included into the list of alchemic elements together with mercury as a “basis of metallicity” and the rock salt as a “basis of constancy”. As a result it was acknowledged for a chemical element in modern sense with a delay. Sulfur was not considered a chemical element until the decline of oxygen theory of acids, for the same reason, for which a long time chlorine also was not acknowledged to be a chemical element: as compounds of S and Cl with hydrogen are acids. Only after the proof of the elementary nature of Cl elementary nature of sulfur was finally acknowledged.
The German and Scandinavian words for sulfur (schwefel/svovel/svavl) were derived from the Indo-European suelphlos,which is derived from swel, meaning “to burn slowly”. The Latin sulpur may have the same origin. Sulfur is also thought to have been derived from Sanskrit sulveri, meaning the enemy of copper. The Greeks burnt elemental sulfur to ‘purify the atmosphere’ and recognized its usefulness in medicine. Brimstone was a major force in the destruction of Sodom and Gomorrah.
From the thirteenth to the mid-nineteenth century, gunpowder (made from NaNO3, charcoal, and sulfur in 75:15:10 weight ratio) was important in military affairs although, later on, it was replaced by nitroglycerine and cordite.
Metal sulfides were among the earliest inorganic pigments (e.g. ultramarine). The alchemists regarded metals as derived from sulfur and mercury, with higher sulfur contents resulting in less metallic properties.
Selenium. Selenium was discovered in 1817 by Jöns Jakob Berzelius. He studied deposits appeared in lead chambers at H2SO4 production by the nitrosyl (lead chamber) process. Selenium derived its name from the Greek word meaning “Moon”).
Tellurium. Elemental tellurium was known for a long time and in the 18th century it was discovered in natural ore containing gold and tellurium (1782). Franz-Joseph Müller von Reichenstein (Müller Ferenc) studied this ore from Transylvania for a few years. He concluded after a thorough investigation that the ore contained mainly gold and an unknown metal very similar to antimony. He called this metal aurum paradoxium or metallum problematicum. Martin Heinrich Klaproth named the new element in 1798 after the Latin word for "earth", tellus. Only in 1832 J. Berzelius found its analogy with non-metallic Se and S.
Martin Heinrich Klaproth
Polonium is a radioactive chemical element with atomic number 84 and the symbol Po. Its existence was foreseen by D. Mendeleyev in 1870. In 1898, Marie Skłodowska-Curie and Pierre Curie discovered this chemical element studying radioactivity of “pitchblende” (uranium ore Uraninite; from pitch, because of its black color, and blende, a term used by German miners to denote minerals whose density suggested metal content, but whose exploitation was, at the time they were named, either impossible or not economically feasible). Also tentatively called "Radium F", it was later named after Marie Curie's native land of Poland (Latin: Polonia).
Marie Skłodowska-Curie (1867-1934) and Pierre Curie (1859-1906)