Niobium

Niobium react with oxygen, O₂, passivating the surface.

Niobium is resistant to most acids. It does dissolve in hydrofluoric acid, HF, or a mixture of HF and nitric acid, HNO₃.

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]

Niobium does not react with water under normal conditions.