Reaction of technetium with acids
Technetium is insoluble in hydrochloric acid (HCl) and hydrofluoric acid (HF). It does dissolve in nitric acid, HNO3, and concentrated sulphuric acid, H2SO4, forming solutions of pertechnetic acid, HTcO4.
Reaction of technetium with air
Technetium tarnishes very slowly in moist air, and upon heating with oxygen, O2, forms technetium(VII) oxide, Tc2O7.
4 Tc(s) + 7 O2(g) 2 Tc2O7(s)
Reaction of technetium with halogens
Technetium reacts with fluorine upon heating, forming a mixture of Tc(IV) and Tc(VII) fluoride.
Tc(s) + 3 F2(g) TcF6(s)
2 Tc(s) + 7 F2(g) 2 TcF7(s)
Reaction of technetium with water
Technetium reacts with water :
Tc(s) + 2 H2O(l) TcO2(s) + 4 H+(aq) + 4 e− E° = -0.272 V
TcO2(s) + H2O(l) TcO3(s) + 2 H+(aq) + 2 e− E° = -0.757 V
Tc2+(aq) + 4 H2O(l) TcO4−(aq) + 8 H+(aq) + 5 e− E° = -0.500 V