LanthanideElement 67 · f-block

Holmium (Ho)

Holmium (Ho) is a lanthanide with atomic number 67 and a standard atomic weight of 164.93. At room temperature it is a solid that melts at 1,472 °C and boils at 2,700 °C.

67HoHolmium164.93

Atomic number

protons

Atomic weight

164.93

CIAAW 2024

Melting point

1,472 °C

1,745.15 K

Boiling point

2,700 °C

2,973.15 K

Density

8.8 g/cm³

near room temperature

Electronegativity

1.23

Pauling scale

State at 25 °C

Solid

Discovered

1878

Switzerland / Sweden

Holmium at a glance

Identity

Symbol	Ho
Atomic number (Z)	67
Atomic weight	164.93 ± 0.01 (CIAAW 2024)
Category	Lanthanide
Group	— (f-block: lanthanide series)
Period	6
Block	f-block
CAS number	7440-60-0

Atomic properties

Electron configuration	[Xe] 4f¹¹ 6s² Full: 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 4f¹¹ 5s² 5p⁶ 6s²
Electrons per shell	2, 8, 18, 29, 8, 2
Oxidation states	+3 Less common: 0, +1, +2
Electronegativity (Pauling)	1.23
First ionisation energy	6.021 eV (581 kJ/mol) 2nd: 11.781 eV · 3rd: 22.79 eV
Atomic radius (empirical)	175 pm
Covalent radius	166 pm
Van der Waals radius	230 pm

Physical properties

State at 25 °C	Solid
Melting point	1,472 °C · 2,681.6 °F · 1,745.15 K
Boiling point	2,700 °C · 4,892 °F · 2,973.15 K
Density	8.8 g/cm³
Specific heat capacity	0.165 J/(g·K)
Crystal structure	Hexagonal

Isotopes & abundance

Natural occurrence	Primordial
Radioactive	No
Natural isotopes (abundance)	¹⁶⁵Ho 100%
Stable isotopes	1
Known isotopes	39
Abundance in Earth's crust	1.3 mg/kg
Abundance in seawater	0.00000022 mg/L

Atomic weights: CIAAW Abridged Standard Atomic Weights 2024. Other properties: standard reference compilations, checked October 2026; predicted values are marked.

Holmium electron configuration

Holmium has 67 electrons. Written in short form, its ground-state configuration is [Xe] 4f¹¹ 6s² — the electrons of the noble gas xenon, plus 4f¹¹ 6s².Written out in full: 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 4f¹¹ 5s² 5p⁶ 6s².

4f↑↓↑↓↑↓↑↓↑↑↑

6s↑↓

Discovery and name

Discovered

1878 — Marc Delafontaine and Jacques-Louis Soret; independently Per Teodor Cleve (1879) · Switzerland / Sweden.

Name

Latin Holmia, Stockholm.

Known for

Has the highest magnetic strength of any element and is used in powerful magnet pole pieces and holmium lasers for surgery.

Isotopes of holmium

Naturally occurring holmium is a mix of 1 isotope. Each has 67 protons; they differ in the number of neutrons:

Isotope	Protons	Neutrons	Natural abundance	Stability
¹⁶⁵Ho	67	98	100%	stable

39 isotopes of holmium are known in our data set (half-lives as published in nuclear data tables).

Holmium and its neighbours in the lanthanide series

Neighbouring elements in the same f-block series:

Element	Z	Atomic weight	Melting point	Boiling point	Density	Electronegativity
Gadolinium	64	157.25	1,313 °C	3,273 °C	7.9 g/cm³	1.2
Terbium	65	158.93	1,359 °C	3,230 °C	8.23 g/cm³	1.1
Dysprosium	66	162.50	1,412 °C	2,567 °C	8.55 g/cm³	1.22
Holmium	67	164.93	1,472 °C	2,700 °C	8.8 g/cm³	1.23
Erbium	68	167.26	1,529 °C	2,868 °C	9.07 g/cm³	1.24
Thulium	69	168.93	1,545 °C	1,950 °C	9.321 g/cm³	1.25
Ytterbium	70	173.05	824 °C	1,196 °C	6.9 g/cm³	1.1

Frequently asked questions

6 answers

What is the atomic mass of holmium?

The standard atomic weight of holmium is 164.93 ± 0.01 (CIAAW 2024), so one mole weighs about 164.93 grams.

How many protons, neutrons and electrons does holmium have?

A neutral holmium atom has 67 protons and 67 electrons. Its most common isotope, holmium-165, has 98 neutrons.

What is the electron configuration of holmium?

[Xe] 4f¹¹ 6s² (in full: 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 4f¹¹ 5s² 5p⁶ 6s²).

What are the melting and boiling points of holmium?

Holmium melts at 1,472 °C (2,681.6 °F) and boils at 2,700 °C (4,892 °F).

Is holmium a metal?

Holmium is a metal. It is in the f-block, period 6, and is a solid at room temperature.

Who discovered holmium?

1878 — Marc Delafontaine and Jacques-Louis Soret; independently Per Teodor Cleve (1879) (Switzerland / Sweden).