Terbium (Tb)
Lanthanide
Terbium is a scarce rare earth whose compounds glow intense green — one third of the trio behind white fluorescent lighting and colour displays. An alloy of terbium changes shape in magnetic fields, turning any surface into a speaker.
Position on the periodic table
Atomic properties
| Atomic number | 65 |
|---|---|
| Atomic mass | 158.925 amu |
| Electron configuration | 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 5p6 6s2 4f9 |
| Noble gas shorthand | [Xe] 4f9 6s2 |
| Electrons per shell | 2, 8, 18, 27, 8, 2 |
| Valence electrons (outer shell) | 2 |
| Common oxidation states | +3, +4 |
| Electronegativity (Pauling) | 1.1 |
| Covalent radius (approx.) | 194 pm |
| First ionization energy | 565.8 kJ/mol |
| Electron affinity | 112.4 kJ/mol |
Physical properties
| State at 25 °C | Solid |
|---|---|
| Density | 8.23 g/cm³ |
| Melting point | 1355.8 °C (1629 K) |
| Boiling point | 3122.8 °C (3396 K) |
| Appearance | silvery white |
| Radioactive | No |
| Origin | Occurs naturally |
Electron configuration of terbium
Terbium's ground-state electron configuration is 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 5p6 6s2 4f9, usually shortened to [Xe] 4f9 6s2. Its electrons occupy 6 shells (2, 8, 18, 27, 8, 2), placing it in period 6 of the f-block. Explore it interactively in the electron configuration calculator.
Uses of terbium
- Green phosphors in lamps and displays
- Magnetostrictive actuators (Terfenol-D)
- Fuel-cell stabilisers
Biological role: None known.
Occurrence: Among the scarcer rare earths; from ion-adsorption clays and monazite.
Common compounds of terbium
Tb4O7
Terbium oxide
History and discovery
Discovered: 1843 — Carl Gustaf Mosander. Name origin: Named after Ytterby, Sweden — one of four elements honouring the same village.
Carl Gustaf Mosander separated terbium from yttrium earth in 1843.
Safety notes
Low toxicity; typical rare-earth precautions.
Educational context only — always follow your school's laboratory rules and never handle chemicals without proper supervision. See our disclaimer.
Practice questions
Quick practice: Terbium
1. What is the chemical symbol of Terbium?
2. What is the atomic number of Terbium?
3. Which category does Terbium belong to?
4. What is the state of Terbium at room temperature?
5. Which period of the periodic table is Terbium in?
Terbium FAQs
What is the atomic number of terbium?
Terbium's atomic number is 65 — every terbium atom has 65 protons in its nucleus.
What is the symbol for terbium?
Tb. Named after Ytterby, Sweden — one of four elements honouring the same village.
Is terbium a metal, nonmetal, or metalloid?
Terbium is classified as a lanthanide.
What state is terbium at room temperature?
At about 25 °C, terbium is a solid. It melts at 1355.8 °C.
What is terbium used for?
Key uses include: green phosphors in lamps and displays; magnetostrictive actuators (terfenol-d); fuel-cell stabilisers.
Related elements
Keep working with this element
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