Terbium
Definition and meaning of Terbium in chemistry.
![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.](/assets/images/terms/terbium-chemical-element.webp)
Terbium is a chemical element with the symbol Tb and atomic number 65. It is a silvery-white, rare-earth metal that is soft enough to cut with a knife. Terbium remains relatively stable in air compared to other highly reactive lanthanide metals. You will never find it in nature as a free element.
In more detail
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.
Key facts
| Field | General Chemistry |
|---|---|
| Symbol | Tb |
| Atomic number | 65 |
| Atomic mass | 158.93 u |
| Category | Lanthanide |
| Year discovered | 1843 |
Manufacturers heavily use terbium oxide in the bright green phosphors for fluorescent lamps. It provides the essential green component of the standard trichromatic lighting system. Engineers also use terbium in naval sonar systems and highly sensitive chemical sensors.
Frequently asked questions
What is the primary use of terbium?
Its most significant use is in green phosphors for fluorescent lamps and electronic displays. It is also a key ingredient in an alloy called Terfenol-D. This special alloy expands or contracts when placed in a magnetic field.
Is terbium a rare element?
Yes, it is one of the rarest of all the lanthanide elements. This scarcity makes the pure metal relatively expensive and quite difficult to isolate.
Related terms
Sources & references
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