Samarium: reactions of elements
Reaction of samarium with air
Samarium metal tarnishes slowly in air and burns readily to form samarium (III) oxide, Sm2O3.
4Sm + 3O2 → 2Sm2O3
Reaction of samarium with water
The silvery white metal samarium is quite electropositive and reacts slowly with cold water and quite quickly with hot water to form samarium hydroxide, Sm(OH)3, and hydrogen gas (H2).
2Sm(s) + 6H2O(g) → 2Sm(OH)3(aq) + 3H2(g)
Reaction of samarium with the halogens
Samarium metal reacts with all the halogens to form samarium(III) halides. So, it reacts with fluorine, F2, chlorine, Cl2, bromine, I2, and iodine, I2, to form respectively samarium(III) bromide, SmF3, samarium(III) chloride, SmCl3, samarium(III) bromide, SmBr3, and samarium(III) iodide, SmI3.
2Sm(s) + 3F2(g) → 2SmF3(s) [white]
2Sm(s) + 3Cl2(g) → 2SmCl3(s) [yellow]
2Sm(s) + 3Br2(g) → 2SmBr3(s) [yellow]
2Sm(s) + 3I2(g) → 2SmI3(s) [orange]
Reaction of samarium with acids
Samarium metal dissolves readily in dilute sulphuric acid to form solutions containing the yellow aquated Sm(III) ion together with hydrogen gas, H2. It is quite likely that Sm3+(aq) exists as largely the complex ion [Sm(OH2)9]3+
2Sm(s) + 3H2SO4(aq) → 2Sm3+(aq) + 3SO42-(aq) + 3H2(g)