Reaction of niobium with air
Niobium react with oxygen, O2, passivating the surface.
Reaction of niobium with acids
Niobium is resistant to most acids. It does dissolve in hydrofluoric acid, HF, or a mixture of HF and nitric acid, HNO3.
Reaction of niobium with halogens
Niobium reacts with all the halogens, forming the corresponding niobium(V) halides.
2 Nb(s) + 5 F2(g) 2 NbF5(s) [white]
2 Nb(s) + 5 Cl2(g) 2 NbCl5(l) [yellow]
2 Nb(s) + 5 Br2(g) 2 NbBr5(s) [orange]
2 Nb(s) + 5 I2(g) 2 NbI5(s) [brass coloured]
Reaction of niobium with water
Niobium does not react with water under normal conditions.