065Lanthanide · Group 3 · Period 6

Terbium

Terbium (Tb) is element 65, a lanthanide in the f-block — group 3, period 6. It is a solid at room temperature with 6 electron shells (2, 8, 18, 27, 8, 2) and an atomic mass of 158.925352 u.

Atomic mass: 158.9 u
Phase · STP: solid
Melting: 1629 K · 1356 °C
Boiling: 3396 K · 3123 °C
Electronegativity: 1.1
Density: 8.23 g/cm³

Photograph — Unknown authorUnknown author, CC BY 1.0 <https://creativecommons.org/licenses/by/1.0>, via Wikimedia Commons, source: https://images-of-elements.com/terbium.php

Identity

Atomic number: 65
Standard atomic weight: 158.9 u
Category: Lanthanide
Group: 3
Period: 6
Block: f-block
Oxidation states: +3

Physical properties

Melting point: 1629 K · 1356 °C
Boiling point: 3396 K · 3123 °C
Density: 8.23 g/cm³
Molar heat capacity: 28.91 J/(mol·K)
Atomic radius: 221 pm
Electron affinity: 112.4 kJ/mol

Atomic structure

65protons

94neutrons

65electrons

2valence e⁻

Noble-gas notation: [Xe] 4f9 6s2
Full configuration: 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 5p6 6s2 4f9
Electrons per shell: 2, 8, 18, 27, 8, 2

Periodic trends

Where Terbium ranks across all 118 elements.

Electronegativity1.1

Ionization energy565.8 kJ/mol

Electron affinity112.4 kJ/mol

Density8.23 g/cm³

Atomic radius221 pm

Ionization energies

Energy to remove each successive electron (kJ/mol).

565.8

1.1k

2.1k

3.8k

Successive ionization energies (kJ/mol, log scale).

Discovery

Discovered: 1843
Discovered by: Carl Gustaf Mosander
Named by: —
Appearance: silvery white