Terbium (Tb) – element 65
Terbium is a chemical element with the symbol Tb and atomic number 65. It is a lanthanide in group 3 (lanthanides), period 6 of the periodic table (f-block), and is a solid at room temperature.
Terbium (Tb) has atomic number 65, atomic mass 158.93 u and electron configuration [Xe] 4f9 6s2.
Terbium facts
| Symbol | Tb |
|---|---|
| Atomic number | 65 |
| Atomic mass | 158.93 u (g/mol) |
| Category | lanthanide |
| Group | group 3 (lanthanides) |
| Period | 6 |
| Block | f-block |
| Phase at 20 °C | Solid |
| Electron configuration | 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 5p6 6s2 4f9 |
| Noble-gas notation | [Xe] 4f9 6s2 |
| Electrons per shell | 2, 8, 18, 27, 8, 2 |
Bohr model and shells
Terbium has 65 electrons in 6 shells: 2, 8, 18, 27, 8, 2. Full configuration and noble-gas notation are in the table; work out any element or ion with the electron configuration calculator.
Physical and atomic properties
| Melting point | 1629 K (1355.8 °C) |
|---|---|
| Boiling point | 3396 K (3122.8 °C) |
| Density | 8.23 g/cm³ |
| Electronegativity (Pauling) | 1.1 |
| Electron affinity | 112.4 kJ/mol |
| Ionization energies | 565.8, 1110, 2114 kJ/mol (1st, 2nd, 3rd) |
| Molar heat capacity | 28.91 J/(mol·K) |
| Discovered by | Carl Gustaf Mosander |
Use the atomic mass in the molar mass calculator for any formula containing Tb.
Position in the periodic table
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Frequently asked questions
What is the atomic mass of terbium?
The atomic mass of terbium is 158.93 u, so one mole of terbium atoms weighs 158.93 g.
What is the electron configuration of terbium?
Terbium has 65 electrons: 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶ 5s² 4d¹⁰ 5p⁶ 6s² 4f⁹, or [Xe] 4f⁹ 6s² in noble-gas notation. Electrons per shell: 2, 8, 18, 27, 8, 2.
Is terbium a metal?
Yes. Terbium is a lanthanide.
Where is terbium on the periodic table?
Terbium is in group 3 (lanthanides), period 6, in the f-block.
Data: Periodic-Table-JSON (CC BY-SA 3.0); standard atomic weights from IUPAC (abridged). Values in brackets are the mass number of the longest-lived isotope.