Terbium

Terbium dissolves readily in dilute sulphuric acid, forming a very pale pink solution of Tb(III) ions and hydrogen gas, H₂.

2 Tb(s) + 3 H₂SO₄(aq) 2 Tb³⁺(aq) + 3 SO₄²⁻(aq) + 3 H₂(g)

Terbium tarnishes slowly in air and burns readily, forming terbium oxides (no reference to composition yet).

Terbium reacts with the halogens, forming the corresponding terbium(III) halides:

2 Tb(s) + 3 F₂(g) 2 TbF₃(s) [white]
2 Tb(s) + 3 Cl₂(g) 2 TbCl₃(s) [white]
2 Tb(s) + 3 Br₂(g) 2 TbBr₃(s) [white]
2 Tb(s) + 3 I₂(g) 2 TbI₃(s) [yellow]

Terbium reacts slowly with cold water, and quickly with hot water, forming terbium(III) hydroxide, Tb(OH)₃, and hydrogen gas, H₂

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