![Terbium element card: symbol Tb, atomic number 65, atomic mass 158.93, electron configuration [Xe] 4f⁹ 6s², oxidation states +3, Lanthanide, f-block, period 6, solid at room temperature.](https://stage.chemistry-dictionary.com/wp-content/uploads/2026/09/terbium-chemical-element.webp)
Terbium naturally occurs in minerals such as cerite, gadolinite, and monazite. Chemists separate it from other rare-earth elements using a process called solvent extraction. Terbium is positioned among the heavy lanthanides in the f-block of the periodic table.
The element is famous for its brilliant green phosphorescence. It glows brightly when excited by strong electron beams or ultraviolet light. Terbium is an electropositive metal that reacts slowly with cold water.
It reacts much more quickly with hot water to form terbium hydroxide and hydrogen gas. In its compounds, terbium primarily exists in the +3 oxidation state. However, the +4 state also exists in specific compounds like terbium(IV) oxide.
This unique oxide appears as a dark maroon or completely black solid. Terbium is highly valued for its role in solid-state devices and advanced lighting phosphors. This demand remains high despite it being one of the least abundant rare-earth elements.
The metal also displays interesting magnetic properties at different temperatures. It undergoes a ferromagnetic ordering at extremely low temperatures. As the temperature increases, it transitions to an antiferromagnetic state and eventually becomes paramagnetic.