Rhenium: reactions of elements
Reaction of rhenium with air
Rhenium is less reactive to air than manganese, which is two places above rhenium in the periodic table. It is about as reactive as technetium metal, which is immediately above rhenium in the periodic table. As such it tarnishes only very slowly in moist air. In practice, rhenium is often supplied as a powder or as a sponge, and in this form it is much more reactive. When heated with oxygen the result is rhenium (VII) oxide, (rhenium heptoxide, Tc2O7).
4Re(s) + 7O2(g) → 2Re2O7(s)
Reaction of rhenium with water
Rhenium does not react with water under normal conditions.
Reaction of rhenium with the halogens
In similar fashion to technetium, immediately above rhenium in the periodic table, rhenium is often supplied as a powder or as a sponge, and in this form it is quite more reactive. When heated with fluorine the result is a mixture of rhenium (VI) fluoride, (rhenium hexafluoride, TcF6) and rhenium (VII) fluoride, (rhenium heptafluoride, ReF7).
Re(s) + 3F2(g) → ReF6(s)
2Re(s) + 7F2(g) → 2ReF7(s)
If the fluorine burn reaction is carried out under pressure at 400°C, the sole product is rhenium heptafluoride, TcF7.
Rhenium metal does dissolve in warm bromine water.
Reaction of rhenium with acids
In similar fashion to technetium, immediately above rhenium in the periodic table, rhenium is insoluble in hydrochloric acid (HCl) and hydrofluoric acid (HF). It does dissolve in nitric acid, HNO3, or concentrated sulphuric acid, H2SO4, both of which are oxidizing, to form solutions of perrhenic acid, HReO4. In this form, the rhenium is in the formal +7 oxidation state.