---
title: "Terbium (Tb) — element 65"
description: "Terbium is element 65, symbol Tb, atomic weight 158.93. Configuration, properties, uses and neighbours."
url: https://atoneplace.net/element/terbium/
site: "At One Place"
---

# Terbium (Tb)

**Terbium — element 65: Tb**

158.93 u · Lanthanide · period 6

Terfenol-D, an alloy of terbium, dysprosium and iron, changes length by about 0.2% in a magnetic field — an enormous magnetostriction that lets it act as a solid-state actuator or turn any flat surface into a loudspeaker. Terbium is one of the four elements named after Ytterby in Sweden, along with yttrium, erbium and ytterbium, all from the same small quarry. Adding a few percent of terbium to a neodymium magnet raises the temperature it can work at, which is why electric car motors consume more of it than anything else.

## Properties

- **Atomic number:** 65
- **Symbol:** Tb
- **Standard atomic weight:** 158.93 u
- **Category:** Lanthanide
- **Period:** 6
- **Block:** f-block
- **Electron configuration:** [Xe] 6s² 4f⁹
- **Electrons per shell:** 2, 8, 18, 27, 8, 2
- **Melting point:** 1,629 K — 1355.8 °C — 2472.5 °F
- **Boiling point:** 3,503 K — 3229.8 °C — 5845.7 °F
- **Density:** 8.23 g/cm³
- **Oxidation states:** +3
- **Discovered:** 1843 by Carl Gustaf Mosander

## Electron configuration

- **Full:** 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶ 5s² 4d¹⁰ 5p⁶ 6s² 4f⁹
- **Noble gas shorthand:** [Xe] 6s² 4f⁹
- **Shells:** K: 2 · L: 8 · M: 18 · N: 27 · O: 8 · P: 2

## What it is used for

- Green phosphors in fluorescent lamps and LED lighting
- Terfenol-D magnetostrictive actuators and sonar transducers
- Raising the working temperature of neodymium magnets
- X-ray intensifying screens

> No Pauling electronegativity is listed in the standard tables for terbium.

## Neighbours in the table

| Z | Element | Symbol | Mass |
| --- | --- | --- | --- |
| 63 | Europium | Eu | 151.96 |
| 64 | Gadolinium | Gd | 157.25 |
| 65 | Terbium ← | Tb | 158.93 |
| 66 | Dysprosium | Dy | 162.5 |
| 67 | Holmium | Ho | 164.93 |

## Common questions

### What is the atomic number of terbium?

65. That is the number of protons in its nucleus, which is what defines the element.

### What is the symbol for terbium?

Tb.

### What is the electron configuration of terbium?

1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶ 5s² 4d¹⁰ 5p⁶ 6s² 4f⁹, or [Xe] 6s² 4f⁹ in noble-gas shorthand.

### What is the melting point of terbium?

1,629 K — 1355.8 °C — 2472.5 °F

## Related pages

- [Europium (Eu)](https://atoneplace.net/element/europium/)
- [Gadolinium (Gd)](https://atoneplace.net/element/gadolinium/)
- [Dysprosium (Dy)](https://atoneplace.net/element/dysprosium/)
- [Holmium (Ho)](https://atoneplace.net/element/holmium/)

## Sources

- Official vendor product documentation — At One Place (/about/)