Lanthanum - ₅₇La: reactions of elements

Reaction of lanthanum with air

Lanthanum metal tarnishes slowly in air and burns readily to form lanthanum (III) oxide, La₂O₃.

4La + 3O₂ → 2La₂O₃

Reaction of lanthanum with water

The silvery white metal lanthanum is quite electropositive and reacts slowly with cold water and quite quickly with hot water to form lanthanum hydroxide, La(OH)₃, and hydrogen gas (H₂).

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

Reaction of lanthanum with the halogens

Lanthanum metal reacts with all the halogens to form lanthanum(III) halides. So, it reacts with fluorine, F₂, chlorine, Cl₂, bromine, I₂, and iodine, I₂, to form respectively lanthanum(III) bromide, LaF₃, lanthanum(III) chloride, LaCl₃, lanthanum(III) bromide, LaBr₃, and lanthanum(III) iodide, LaI₃.

2La(s) + 3F₂(g) → 2LaF₃(s)

2La(s) + 3Cl₂(g) → 2LaCl₃(s)

2La(s) + 3Br₂(g) → 2LaBr₃(s)

2La(s) + 3I₂(g) → 2LaI₃(s)

Reaction of lanthanum with acids

Lanthanum metal dissolves readily in dilute sulphuric acid to form solutions containing the aquated La(III) ion together with hydrogen gas, H₂. It is quite likely that La³⁺(aq) exists as largely the complex ion [La(OH₂)₉]³⁺

2La(s) + 3H₂SO₄(aq) → 2La³⁺(aq) + 3SO₄^2-(aq) + 3H₂(g)

Reaction of lanthanum with bases