Chemical reactions of the elements
Reaction of europium with air
Europium metal tarnishes slowly in air and burns readily to form europium (III) oxide, Eu2O3.
4Eu + 3O2 → 2Eu2O3
Reaction of europium with water
The silvery white metal europium is quite electropositive and reacts slowly with cold water and quite quickly with hot water to form europium hydroxide, Eu(OH)3, and hydrogen gas (H2).
2Eu(s) + 6H2O(g) → 2Eu(OH)3(aq) + 3H2(g)
Reaction of europium with the halogens
Europium metal reacts with all the halogens to form europium(III) halides. So, it reacts with fluorine, F2, chlorine, Cl2, bromine, I2, and iodine, I2, to form respectively europium(III) bromide, EuF3, europium(III) chloride, EuCl3, europium(III) bromide, EuBr3, and europium(III) iodide, EuI3. There are question marks regarding the existence of europium(III) iodide.
2Eu(s) + 3F2(g) → 2EuF3(s) [white]
2Eu(s) + 3Cl2(g) → 2EuCl3(s) [yellow]
2Eu(s) + 3Br2(g) → 2EuBr3(s) [grey]
2Eu(s) + 3I2(g) → 2EuI3(s) [?]
Reaction of europium with acids
Europium metal dissolves readily in dilute sulphuric acid to form solutions containing the very pale pink aquated Eu(III) ion together with hydrogen gas, H2. It is quite likely that Eu3+(aq) exists as largely the complex ion [Eu(OH2)9]3+
2Eu(s) + 3H2SO4(aq) → 2Eu3+(aq) + 3SO42-(aq) + 3H2(g)
Reaction of europium with bases