---
title: "Erbium (Er) — element 68"
description: "Erbium is element 68, symbol Er, atomic weight 167.26. Configuration, properties, uses and neighbours."
url: https://atoneplace.net/element/erbium/
site: "At One Place"
---

# Erbium (Er)

**Erbium — element 68: Er**

167.26 u · Lanthanide · period 6

Every transoceanic fibre-optic cable depends on erbium. An erbium-doped fibre amplifier boosts a light signal directly, without converting it to electricity and back, and it happens to amplify at 1,550 nm — precisely the wavelength where silica fibre is most transparent. That coincidence, exploited from about 1990, is what made long-haul optical networking economic, and therefore what made the modern internet affordable.

## Properties

- **Atomic number:** 68
- **Symbol:** Er
- **Standard atomic weight:** 167.26 u
- **Category:** Lanthanide
- **Period:** 6
- **Block:** f-block
- **Electron configuration:** [Xe] 6s² 4f¹²
- **Electrons per shell:** 2, 8, 18, 30, 8, 2
- **Melting point:** 1,802 K — 1528.8 °C — 2783.9 °F
- **Boiling point:** 3,141 K — 2867.8 °C — 5194.1 °F
- **Density:** 9.07 g/cm³
- **Electronegativity:** 1.24 (Pauling)
- **Oxidation states:** +3
- **Discovered:** 1843 by Carl Gustaf Mosander

## Electron configuration

- **Full:** 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶ 5s² 4d¹⁰ 5p⁶ 6s² 4f¹²
- **Noble gas shorthand:** [Xe] 6s² 4f¹²
- **Shells:** K: 2 · L: 8 · M: 18 · N: 30 · O: 8 · P: 2

## What it is used for

- Erbium-doped fibre amplifiers, which carry the internet across oceans
- Er:YAG lasers for dermatology and dentistry
- Pink colouring in glass, glazes and cubic zirconia
- Neutron-absorbing burnable poison in reactor fuel

## Neighbours in the table

| Z | Element | Symbol | Mass |
| --- | --- | --- | --- |
| 66 | Dysprosium | Dy | 162.5 |
| 67 | Holmium | Ho | 164.93 |
| 68 | Erbium ← | Er | 167.26 |
| 69 | Thulium | Tm | 168.93 |
| 70 | Ytterbium | Yb | 173.05 |

## Common questions

### What is the atomic number of erbium?

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

### What is the symbol for erbium?

Er.

### What is the electron configuration of erbium?

1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶ 5s² 4d¹⁰ 5p⁶ 6s² 4f¹², or [Xe] 6s² 4f¹² in noble-gas shorthand.

### What is the melting point of erbium?

1,802 K — 1528.8 °C — 2783.9 °F

## Related pages

- [Dysprosium (Dy)](https://atoneplace.net/element/dysprosium/)
- [Holmium (Ho)](https://atoneplace.net/element/holmium/)
- [Thulium (Tm)](https://atoneplace.net/element/thulium/)
- [Ytterbium (Yb)](https://atoneplace.net/element/ytterbium/)

## Sources

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