Group 7 (VIIB): Mn, Tc, Re, Bh
This page contains brief profiles and pictures of each of the Group 7 metals (VIIB). More information can be found via the WWW links following each element. However, as these links are to other servers on the Internet you will need to use the BACK button on your browser to return to this page. Credits for the photos and principal links can be found at the end of this document.
The name of the 25th element comes from the Latin magnes, meaning magnet. It was discovered in 1774 by Scheele and isolated later that year by Johan Gahn.
In pure form Manganese is a hard, brittle, gray-white metal. It is best known as an alloying agent in steel. It enhances the ability to hot-work steel and increases resistance to impact. In biological systems manganese is a crucial component of vitamin B1.
The pure metal is produced from its most common compound (MnO2---10th most abundant compound in the earth's crust). It can be reduced chemically or refined electrolytically. The element has at least 5 stable oxidation states with distinctive colors (as is typical of transition metals). It is commonly encountered in the laboratory as the compound KMnO4 which is a strong oxidizing agent. MnO2 catalyzes the decomposition of H2O2 and is sometimes used for the small scale production of oxygen gas in the lab.More background information on Mn More data on Mn
Technetium has the distinction of being the first synthetically produced element. It was the last of the six elements predicted by Mendeleev to be discovered (in 1937 by SegrÃ¨ and Perrier). Trace amounts were found in a sample of molybdenum that had been bombarded with deuterons in a cyclotron.
All known isotopes of Tc are radioactive and none appears to occur naturally on earth. However, it is produced commercially in kg quantities because very tiny amounts (55 parts per million) can transform iron into a corrosion resistant alloy. All applications of the metal involve closed systems, however, because of the radioactivity.
Pure Tc is a silvery-gray metal similar in appearance to platinum but it is normally produced in powdered form. Chemically it resembles a cross between Mn and Re. Although of little interest, compounds have been prepared in which Tc exhibits oxidation states of +4, +6 and +7.More background information on Tc More data on Tc
A dense, silvery white metal, Rhenium takes its name from the Latin, Rhenus, for the Rhine river. It was discovered in 1925 by Ida and Walter Noddack along with Otto Berg. It is nearly twice as dense as lead (21 g/cm3) and extremely rare (1 pound of rhenium per 1000 million pounds of earth!!!). Nonetheless, the total annual U.S. production of Re is almost half a ton. It is used as a trace alloying element for metal components that are subject to constant friction.
Rhenium was another of the "missing" elements proposed by Mendeleev. The first sample was concentrated 100,000 fold from a gadolinium ore sample. Just enough was obtained for a spectroscopic study in which previously unseen lines were observed. The metal is acid resistant and has one of the highest melting points. But its scarcity (and therefore expense) makes practical use limited.More background information on Re More data on Re
Bh no images of Bohrium available
Element 107 (Uns) was first reported by Soviet scientists in 1976. This claim has since been substantiated by German researchers but no name was suggested and so it has been known by its numerical moniker, unnilseptium (107).
Recently, however, a committee of the IUPAC suggested the name Bohrium (after Niels Bohr). This name was finally approved in August 1997.
There are no practical uses for Bohrium. All known isotopes have extremely short half-lives.More background information on Bh More data on Bh
Sources: Photos of the elements were taken from the LIFE Science Library book Matter. Background links go to the Periodic Table created at Los Alamos National Laboratories by Robert Husted. Data links go to the primary site of Mark Winter's WebElements, version 2.0, at the University of Sheffield in the United Kingdom.