The two oxides of Tc2O7 and Re2O7 are formed when metals are heated in air or oxygen. Both are yellow solids. Tc2O7 is more oxidizing than Re2O7 . Both oxides are soluble in water and form HTcO4 and HReO4 which are colourless. They contain TcO4- and ReO4- ions which are tetrahedral. TcO4- and ReO4- are stable in acidic condition.
TcO4- and ReO4- are colourless because the charge transfer band occur at higher energy in the UV region .
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