Terbium (Tb): Electron Configuration, Properties and Uses
Terbium (Tb): Electron Configuration, Properties and Uses
Electron configuration [Xe] 6s2 4f9 · f-block, lanthanide series · period 6 · Ar 158.93
Terbium data
- Atomic number
- 65
- Relative atomic mass
- 158.93
- Group
- – (lanthanide series)
- Period
- 6
- Block
- f
- Category
- Lanthanide
- Electron configuration
- [Xe] 6s2 4f9
- Full configuration
- 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 5p6 6s2 4f9
- Electrons per shell
- 2, 8, 18, 27, 8, 2 (K L M N O P)
- Valence electrons
- 2 (in the outer shell)
- Electronegativity (Pauling)
- no data
- First ionisation energy
- 5.864 eV
- Atomic radius (van der Waals)
- 221 pm
- State at room temperature
- Solid
- Melting point
- 1356 °C
- Boiling point
- 3230 °C
- Density
- 8.23 g/cm³
- Common oxidation states
- +3
- Discovered
- 1843
Source: PubChem (NIH, accessed 13 Nov 2026); atomic mass: IUPAC standard atomic weight.
Electron shell diagram
K 2 · L 8 · M 18 · N 27 · O 8 · P 2
Orbital diagram (outer electrons)
About terbium
Terbium, symbol Tb, is element number 65 in the periodic table. It belongs to the lanthanide series in period 6 (f-block), usually shown below the main table. The element was discovered in 1843. Terbium is a solid at room temperature, melting at 1356 °C and boiling at 3230 °C.
Terbium electron configuration
The electron configuration of terbium is 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 5p6 6s2 4f9, or in short [Xe] 6s2 4f9. Its electrons occupy 6 shells: K = 2, L = 8, M = 18, N = 27, O = 8, P = 2. As a lanthanide, terbium fills the 4f subshell. Its outer 6s subshell holds 2 electrons; valence electrons for this series are not assigned by the usual group rule. When it forms cations, electrons leave the outermost subshell first: Tb3+ = [Xe] 4f8.
Filling order: 1s2(2) → 2s2(4) → 2p6(10) → 3s2(12) → 3p6(18) → 4s2(20) → 3d10(30) → 4p6(36) → 5s2(38) → 4d10(48) → 5p6(54) → 6s2(56) → 4f9(65)
Uses of terbium
Well-known applications of terbium include green phosphors, the magnetostrictive alloy Terfenol-D and as an additive for heat-resistant NdFeB magnets.
Safety
Terbium metal is generally safe to handle, but avoid breathing its dust and read the SDS before using Terbium compounds. Always read the safety data sheet (SDS) before working with a chemical.
Other lanthanides
Frequently asked questions
What is the electron configuration of terbium?
The electron configuration of terbium (Tb, atomic number 65) is 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 5p6 6s2 4f9, or [Xe] 6s2 4f9 in short. By shell: 2, 8, 18, 27, 8, 2.
How many valence electrons does terbium have?
Terbium has 2 electrons in its outer shell. For lanthanides and actinides, valence electrons are not assigned by the usual group rule.
Which group and period is terbium in?
Terbium is in the lanthanide series, period 6, f-block.
What is the atomic mass of terbium?
The relative atomic mass of terbium is 158.93. Use it to calculate molar mass with the molar mass calculator.
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