Hafnium

Hafnium is resistant to most mineral acids, under cold conditions. Hafnium is dissolved in hydrofluoric acid, HF, presumably forming fluoro complexes.

Hafnium react slowly with O₂ at room temperature, passivating the surface. Hafnium can burn, and as powder it is classified as a fire hazard.

Hf(s) + O₂(g) HfO₂(s)

Hafnium does not appear to react with bases under normal conditions.

Hafnium metal reacts with all the halogens, when heated, forming the corresponding hafnium(IV) halides.

Hf(s) + 2 F₂(g) HfF₄(s) [white]
Hf(s) + 2 Cl₂(g) HfCl₄(s) [white]
Hf(s) + 2 Br₂(g) HfBr₄(s) [white]
Hf(s) + 2 I₂(g) HfI₄(s) [white]

Hafnium does not react with water under normal conditions.