Manganese
Manganese (25Mn) is graryish white, resembling iron, but is harder and very brittle. The metal is chemically reactive, and decomposes cold water slowly. Manganese is widely distributed throughout the animal kingdom. It is an important trace element and may be essential for utilisation of vitamin B. Manganese is present in quantity the floor of oceans. It is an important component of steel.
Technetium
Since Technetium's (43Tc) discovery, searches for the element technetium in terrestrial materials have been made without success. Technetium has been found in the spectrum of S-, M-, and N-type stars, and its presence in stellar matter is leading to new theories of the production of heavy elements in the stars. Technetium is a silvery-grey metal that tarnishes slowly in moist air. Until 1960, technetium was available only in small amounts. The chemistry of technetium is related to that of rhenium.
Rhenium
Rhenium (75Re) is silvery white with a metallic lustre; its density is exceeded only by that of platinum, iridium, and osmium, and its melting point is exceeded only by that of tungsten and carbon. It has other useful properties. It is expensive but useful as a trace alloying agent.
Bohrium
Bohrium (107Bh) is a radioactive synthetic element that is not present in the environment at all. The German discoverers at GSI proposed the name Nielsbohrium (symbol Ns) after Niels Bohr. IUPAC are happy to name an element after Bohr but suggest bohrium (Bh) on the grounds that the first name of a person does not appear in the names of any other element named after a person. This seems to have been accepted by all concerned.
