ABSTRACT
The Group 7 is composed of three elements: manganese (Mn), technetium (Tc), and rhenium (Re). Only Mn is essential to living organisms. Tc is a by-product of nuclear fuel processing and occurs as unstable radionuclides with variable but mainly short half-lives (from seconds to years). Re is highly dispersed in the environment. All elements of Group 7 have variable valences (Table 12.1) and reveal both lithophile and chalcophile characters.
