Erbium (Er)

Erbium is a lanthanide with atomic number 68, in period 6, in the f-block of the periodic table. Its atomic mass is 167.259 u and its electron configuration is [Xe] 4f¹² 6s². Solid at 25 °C.

Download on theApp Store

Key facts

Atomic number	68
Atomic mass	167.259 u
Category	Lanthanide
Period	6
Group	f-block, no group number
Block	f
Electron configuration	[Xe] 4f¹² 6s²
Electrons per shell	2, 8, 18, 30, 8, 2
Electronegativity (Pauling)	1.24
Oxidation states	+2, +3common in bold
State at 25 °C	Solid
Melting point	1802 K1528.85 °C
Boiling point	3141 K2867.85 °C
Density	9.066 g/cm³

Atomic properties

First ionization energy	6.108 eV
Electron affinity	50 kJ/mol
Atomic radius	178 pm
Covalent radius	189 pm
Van der Waals radius	235 pm
Common ions	Er³⁺
Protons, neutrons, electrons	68, 99, 68

Physical and thermal properties

Molar volume	18.46 cm³/mol
Heat of fusion	19.9 kJ/mol
Heat of vaporization	285 kJ/mol
Specific heat	168 J/(kg·K)
Thermal conductivity	15 W/(m·K)
Thermal expansion	1.22 × 10⁻⁵ K⁻¹
Mohs hardness	1.97
Young’s modulus	70 GPa
Crystal structure	Simple hexagonal
Magnetic type	Paramagnetic

Identification and history

CAS number	7440-52-0
Latin name	Erbium
Discovered by	Carl Gustaf Mosander · 1843
Named by	---

Natural isotopes

Isotope	Mass (u)	Abundance
¹⁶²Er	161.928787	0.139 %
¹⁶⁴Er	163.929208	1.601 %
¹⁶⁶Er	165.930301	33.503 %
¹⁶⁷Er	166.932056	22.869 %
¹⁶⁸Er	167.932378	26.978 %
¹⁷⁰Er	169.935472	14.91 %

Data checked against PubChem (NIH), IUPAC, the NIST Atomic Spectra Database and the IAEA (NUBASE and AME), the same data you see in the app.

A dash (---) means there is no reliable published measurement. The app never makes one up.

See Erbium in the app

Orbital diagram with Hund’s rule, emission spectrum, shell model, every isotope, a real photo, and comparison with any other element. Free, no ads, works offline.

Download on theApp Store