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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Famous quotes containing the word occurrence:
“One is absolutely sickened, not by the crimes that the wicked have committed, but by the punishments that the good have inflicted; and a community is infinitely more brutalised by the habitual employment of punishment than it is by the occasional occurrence of crime.”
—Oscar Wilde (1854–1900)