65158.93TbTerbium
Terbium (Tb) — element 65lanthanide · period 6
Terbium is a chemical element with the symbol Tb and atomic number 65. It is a lanthanide in period 6 of the periodic table (the f-block), with a standard atomic mass of 158.93 u. At room temperature (25 °C) terbium is a solid.
💡 Known for: Used in green phosphors and in the magnetostrictive alloy Terfenol-D.
# Terbium properties
| Symbol | Tb |
|---|---|
| Atomic number | 65 |
| Atomic mass | 158.93 u |
| Category | lanthanide |
| Group | — (f-block, no group number) |
| Period | 6 |
| Block | f-block |
| Electron configuration | [Xe] 4f⁹ 6s² |
| Full configuration | 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 4f⁹ 5s² 5p⁶ 6s² |
| Electrons per shell | 2, 8, 18, 27, 8, 2 |
| Protons / electrons | 65 / 65 |
| State at 25 °C | solid |
| Melting point | 1629 K (1355.8 °C, 2472.5 °F) |
| Boiling point | 3503 K (3229.8 °C, 5845.7 °F) |
| Density | 8.229 g/cm³ |
| Electronegativity (Pauling) | 1.1 |
| First ionization energy | 5.864 eV |
| Atomic radius | 225 pm |
| Discovered | 1843 |
# Electron configuration of terbium
The electron configuration of terbium is [Xe] 4f⁹ 6s², written out in full as 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 4f⁹ 5s² 5p⁶ 6s². Its 65 electrons fill 6 shells as 2, 8, 18, 27, 8, 2, so the outermost shell holds 2 electrons.
# Related elements
GdGadoliniumprevious elementDyDysprosiumnext elementLaLanthanumlanthanideCeCeriumlanthanidePrPraseodymiumlanthanideNdNeodymiumlanthanidePmPromethiumlanthanideSmSamariumlanthanideEuEuropiumlanthanideHoHolmiumlanthanide
# Terbium FAQ
What is the atomic number of terbium?
The atomic number of terbium is 65: every terbium atom has 65 protons in its nucleus. Its symbol is Tb.
What is the atomic mass of terbium?
The standard atomic mass of terbium is 158.93 u.
What is the electron configuration of terbium?
Terbium's electron configuration is [Xe] 4f⁹ 6s² (1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 4f⁹ 5s² 5p⁶ 6s²), with 2, 8, 18, 27, 8, 2 electrons per shell.
Is terbium a metal?
Yes. Terbium is a lanthanide, one of the metals.
What is the melting point of terbium?
Terbium melts at 1629 K (1355.8 °C, 2472.5 °F) and boils at 3503 K (3229.8 °C, 5845.7 °F).
What is terbium used for / known for?
Used in green phosphors and in the magnetostrictive alloy Terfenol-D.