Group 7 elements ( Transition Metals)
Group 7,
numbered by IUPAC nomenclature, is a group of elements in the periodic table.
They are manganese (Mn), technetium (Tc), rhenium (Re), and bohrium (Bh).
All known elements of group 7 are transition metals.
All known elements of group 7 are transition metals.
Like other
groups, the members of this family show patterns in their electron
configurations, especially the outermost shells resulting in trends in chemical
behavior.
Chemistry
Z Element No. of electrons/shell
25 manganese 2,
8, 13, 2
43 technetium 2, 8, 18, 13, 2
75 rhenium 2,
8, 18, 32, 13, 2
107 bohrium 2,
8, 18, 32, 32, 13, 2
Bohrium has
not been isolated in pure form, and its properties have not been conclusively
observed; only manganese, technetium, and rhenium have had their properties
experimentally confirmed. All three elements are typical silvery-white
transition metals, hard, and have high melting and boiling points.
History
Group 7
contains the two naturally occurring transition metals discovered last:
technetium and rhenium. Manganese was discovered much earlier owing to its much
larger abundance in nature. Rhenium was discovered when Masataka Ogawa found
what he thought was element 43 in thorianite, but this was dismissed; recent
studies by H. K. Yoshihara suggest that he discovered rhenium instead, a fact
not realized at the time. Walter Noddack, Otto Berg, and Ida Tacke were the
first to conclusively identify rhenium; it was thought they discovered element
43 as well, but as the experiment could not be replicated, it was dismissed.
Technetium was formally discovered in December 1936 by Carlo Perrier and Emilio
Segré, who discovered Technetium-95 and Technetium-97. Bohrium was discovered
in 1981 by a team led by Peter Armbruster and Gottfried Münzenburg by
bombarding Bismuth-209 with Chromium-54.
Occurrence
Manganese is
the only common Group 7 element. In 2007 11 million metric tons of manganese
were mined. All other elements are either incredibly rare on earth (technetium,
rhenium) or completely synthetic (bohrium). In contrast to manganese, only 40
or 50 metric tons of rhenium were mined. Technetium is only found in trace
amounts in nature as a product of spontaneous fission; almost all is produced
in laboratories. Bohrium is only produced in nuclear reactors and has never
been isolated in pure form.
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