Europium

Europium dissolves readily in dilute sulphuric acid, forming Eu(III) ions and hydrogen gas, H₂. The solution is very pale pink and is most likely the complex [Eu(H₂O)₉]³⁺.

2 Eu(s) + 3 H₂SO₄(aq) 2 Eu³⁺(aq) + 3 SO₄²⁻(aq) + 3 H₂(g)

Europium tarnishes slowly in air, and burns readily, forming europium(III) oxide, Eu₂O₃.

4 Eu(s) + 3 O₂(g) 2 Eu₂O₃(s)

Europium reacts with all the halogens, forming the corresponding europium(III) halides.

2 Eu(s) + 3 F₂(g) 2 EuF₃(s) [white]
2 Eu(s) + 3 Cl₂(g) 2 EuCl₃(s) [yellow]
2 Eu(s) + 3 Br₂(g) 2 EuBr₃(s) [grey]
2 Eu(s) + 3 I₂(g) 2 EuI₃(s)

Europium reacts slowly with cold water, and quickly with hot water, forming europium hydroxide, Eu(OH)₃, and hydrogen gas (H₂).

2 Eu(s) + 6 H₂O(g) 2 Eu(OH)₃(aq) + 3 H₂(g)