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About Holmium

Holmium Bohr

In 1878, Marc Delafontain and Jacques-Louis Soret identified spectroscopic absorption bands of an unknown element whose oxide was isolated later that same year by Per Teodor Cleve. All three men are given credit for discovering this new element, which was named holmium after Cleve’s native Stockholm.

Holmium has the greatest magnetic strength of any element, and is used to create extremely strong magnetic fields as a magnetic flux concentrator within high-strength magnets. Holmium is used as a magnet component instead of for fabricating complete magnets because it is extremely rare.

Holmium’s other primary use is as a dopant in garnets, cubic zirconia, and glass. Holmium garnets are used in solid-state lasers that emit at wavelengths that make them safe for use in medical and dental applications, and they are also used in fiber optic communications devices. In glass and cubic zirconia, holmium provides yellow or red coloring and has distinctive absorption peaks that make them useful as calibration standards for optical spectrophotometers. Additionally, the radioactive isotope holmium-166m1 is used to calibrate gamma ray spectrometers.

Holmium is a rare earth element and can be found in any rare earth containing mineral, but as a heavy rare earth element (HREE) it is more common in HREE-enriched minerals such as xenotime and euxenite. Additionally, holmium is present in ion adsorption clays, which are a major source of HREEs due to their relative ease of processing, despite the low percentage quantities of rare earths they contain.

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Elemental Holmium Picture Holmium has the highest magnetic moment (10.6µB) of any naturally occurring element. Because of this, it has been used to create the strongest known magnetic fields by placing it within high-strength magnets as a pole piece or magnetic flux concentrator. This magnetic property is also exploited in holmium-yttrium iron garnet, a synthetic ferrimagnetic material used in microwave and magnetooptical applications. Holmium lases at a human ey-safe 2.08 microns, allowing its use in a variety of medical and dental applications in both yttrium-aluminum-garnet (YAG) and yttrium-lanthanum-fluoride (YLF) solid state lasers. The wavelength High Purity (99.999%) Holmium Oxide (Ho2O3) Powderallows for use in silica fibers designed for shorter wavelengths while still providing the cutting strength of longer wave length equipment. Holmium is available as metal and compounds with purities from 99% to 99.999% (ACS grade to ultra-high purity). Elemental or metallic forms include pellets, rod, wire and granules for evaporation source material purposes. High Purity (99.999%) Holmium (Ho) Sputtering Target Holmium oxides are available in powder and dense pellet form for such uses as optical coating and thin film applications. Oxides tend to be insoluble. Holmium fluoride is another insoluble form for uses in which oxygen is undesirable such as metallurgy, chemical and physical vapor deposition and in some optical coatings. Holmium is also available in soluble forms including chlorides, nitrates and acetates. These compounds can be manufactured as solutions at specified stoichiometries.

Holmium Properties

Holmium (Ho) atomic and molecular weight, atomic number and elemental symbolHolmium is a Block F, Group 3, Period 6 element. Holmium Bohr ModelThe number of electrons in each of Holmium's shells is 2, 8, 18, 29, 8, 2 and its electronic configuration is [Xe] 4f11 6s2. In its elemental form, CAS 7440-60-0, holmium has a silvery white appearance. The holmium atom has a radius of and its Van der Waals radius is unknown. Holmium was first discovered by J.L. Soret in 1878.

Symbol: Ho
Atomic Number: 67
Atomic Weight: 164.93
Element Category: Lanthanide
Group, Period, Block: n/a, 6, f
Color: silvery-white
Other Names: Olmio, Hólmio
Melting Point: 1472°C, 2681.6°F, 1745.15 K
Boiling Point: 2700°C, 4892°F, 2973.15 K
Density: 8.795 g/cm3
Liquid Density @ Melting Point: 8.34 g/cm3
Density @ 20°C: 8.80 g/cm3
Density of Solid: 8795 kg·m3
Specific Heat: 0.0393 Cal/g/ K @ 25 °C
Superconductivity Temperature: N/A
Triple Point: N/A
Critical Point: N/A
Heat of Fusion (kJ·mol-1): 17.2
Heat of Vaporization (kJ·mol-1): 303
Heat of Atomization (kJ·mol-1): 302.63
Thermal Conductivity: 0.162 W/cm/ K @ 298.2 K
Thermal Expansion: (r.t.) (poly) 11.2 µm/(m·K)
Electrical Resistivity: 87.0 nΩ-cm @ 25°C
Tensile Strength: N/A
Molar Heat Capacity: 27.15 J·mol-1·K-1
Young's Modulus: 64.8 GPa
Shear Modulus: 26.3 GPa
Bulk Modulus: 40.2 GPa
Poisson Ratio: 0.231
Mohs Hardness: N/A
Vickers Hardness: 481 MPa
Brinell Hardness: 746 MPa
Speed of Sound: (20 °C) 2760 m·s-1
Pauling Electronegativity: 1.23
Sanderson Electronegativity: N/A
Allred Rochow Electronegativity: 1.1
Mulliken-Jaffe Electronegativity: N/A
Allen Electronegativity: N/A
Pauling Electropositivity: 2.77
Reflectivity (%): N/A
Refractive Index: N/A
Electrons: 67
Protons: 67
Neutrons: 98
Electron Configuration: [Xe] 4f11 6s2
Atomic Radius: 176 pm
Atomic Radius,
non-bonded (Å):
Covalent Radius: 192±7 pm
Covalent Radius (Å): 1.79
Van der Waals Radius: 216 pm
Oxidation States: 3, 2, 1 (basic oxide)
Phase: Solid
Crystal Structure: hexagonal close-packed
Magnetic Ordering: paramagnetic
Electron Affinity (kJ·mol-1) Unknown
1st Ionization Energy: 580.99 kJ·mol-1
2nd Ionization Energy: 1138.54 kJ·mol-1
3rd Ionization Energy: 2203.74 kJ·mol-1
CAS Number: 7440-60-0
EC Number: 231-169-0
MDL Number: MFCD00011049
Beilstein Number: N/A
SMILES Identifier: [Ho]
InChI Identifier: InChI=1S/Ho
PubChem CID: 23988
ChemSpider ID: 22424
Earth - Total: 80 ppb
Mercury - Total: 61 ppb
Venus - Total: 84 ppb
Earth - Seawater (Oceans), ppb by weight: 0.00022
Earth - Seawater (Oceans), ppb by atoms: 0.000008
Earth -  Crust (Crustal Rocks), ppb by weight: 1200
Earth -  Crust (Crustal Rocks), ppb by atoms: 150
Sun - Total, ppb by weight: N/A
Sun - Total, ppb by atoms: N/A
Stream, ppb by weight: 0.01
Stream, ppb by atoms: 0.0001
Meterorite (Carbonaceous), ppb by weight: 60
Meterorite (Carbonaceous), ppb by atoms: 7
Typical Human Body, ppb by weight: N/A
Typical Human Body, ppb by atom: N/A
Universe, ppb by weight: 0.5
Universe, ppb by atom: 0.004
Discovered By: Marc Delafontaine
Discovery Date: 1878
First Isolation: N/A

Health, Safety & Transportation Information for Holmium

Holmium is slightly toxic in its elemental form. Safety data for Holmium and its compounds can vary widely depending on the form. For potential hazard information, toxicity, and road, sea and air transportation limitations, such as DOT Hazard Class, DOT Number, EU Number, NFPA Health rating and RTECS Class, please see the specific material or compound referenced in the Products tab.

Safety Data
Material Safety Data Sheet MSDS
Signal Word Danger
Hazard Statements H228
Hazard Codes F
Risk Codes 11
Safety Precautions N/A
RTECS Number N/A
Transport Information N/A
WGK Germany 3
Globally Harmonized System of
Classification and Labelling (GHS)

Holmium Isotopes

Holmium has one stable isotope: 165Ho.

Nuclide Isotopic Mass Half-Life Mode of Decay Nuclear Spin Magnetic Moment Binding Energy (MeV) Natural Abundance
(% by atom)
140Ho 139.96854(54)# 6(3) ms Unknown 8+# N/A 1093.11 -
141Ho 140.96310(54)# 4.1(3) ms Unknown (7/2-) N/A 1101.18 -
142Ho 141.95977(54)# 400(100) ms ß+ to 142Dy; p to 141Dy (6 to 9) N/A 1118.58 -
143Ho 142.95461(43)# 300# ms [>200 ns] ß+ to 143Dy 11/2-# N/A 1126.66 -
144Ho 143.95148(32)# 0.7(1) s ß+ to 144Dy; ß+ + p to 143Tb N/A N/A 1134.74 -
145Ho 144.94720(32)# 2.4(1) s ß+ to 145Dy (11/2-) N/A 1152.13 -
146Ho 145.94464(21)# 3.6(3) s ß+ to 146Dy; ß+ + p to 145Tb (10+) N/A 1160.21 -
147Ho 146.94006(3) 5.8(4) s ß+ to 147Dy; ß+ + p to 146Tb (11/2-) N/A 1168.29 -
148Ho 147.93772(14) 2.2(11) s ß+ to 148Dy (1+) N/A 1185.68 -
149Ho 148.933775(20) 21.1(2) s ß+ to 149Dy (11/2-) N/A 1193.76 -
150Ho 149.933496(15) 76.8(18) s ß+ to 150Dy 2- N/A 1201.84 -
151Ho 150.931688(13) 35.2(1) s ß+ to 151Dy; a to 147Tb 11/2(-) N/A 1209.92 -
152Ho 151.931714(15) 161.8(3) s ß+ to 152Dy; a to 148Tb 2- N/A 1218 -
153Ho 152.930199(6) 2.01(3) min ß+ to 153Dy; a to 149Tb 11/2- N/A 1226.08 -
154Ho 153.930602(9) 11.76(19) min ß+ to 154Dy; a to 150Tb 2- N/A 1234.16 -
155Ho 154.929103(19) 48(1) min ß+ to 155Dy 5/2+ N/A 1251.55 -
156Ho 155.92984(5) 56(1) min ß+ to 156Dy 4- N/A 1259.63 -
157Ho 156.928256(26) 12.6(2) min ß+ to 157Dy 7/2- N/A 1267.71 -
158Ho 157.928941(29) 11.3(4) min ß+ to 158Dy; a to 154Tb 5+ N/A 1275.79 -
159Ho 158.927712(4) 33.05(11) min ß+ to 159Dy 7/2- N/A 1283.87 -
160Ho 159.928729(16) 25.6(3) min ß+ to 160Dy 5+ N/A 1291.95 -
161Ho 160.927855(3) 2.48(5) h EC to 161Dy 7/2- 4.25 1300.02 -
162Ho 161.929096(4) 15.0(10) min EC to 161Dy 1+ N/A 1308.1 -
163Ho 162.9287339(27) 4570(25) y EC to 161Dy 7/2- 4.23 1316.18 -
164Ho 163.9302335(30) 29(1) min EC to 161Dy; ß- to 164Er 1+ N/A 1314.94 -
165Ho 164.9303221(27) Observationally Stable - 7/2- 4.173 1323.02 100
166Ho 165.9322842(27) 26.83(2) h ß- to 166Er 0- N/A 1331.1 -
167Ho 166.933133(6) 3.003(18) h ß- to 167Er 7/2- N/A 1339.18 -
168Ho 167.93552(3) 2.99(7) min ß- to 168Er 3+ N/A 1347.26 -
169Ho 168.936872(22) 4.72(10) min ß- to 169Er 7/2- N/A 1355.34 -
170Ho 169.93962(5) 2.76(5) min ß- to 170Er 6+# N/A 1363.42 -
171Ho 170.94147(64) 53(2) s ß- to 171Er 7/2-# N/A 1362.18 -
172Ho 171.94482(43)# 25(3) s ß- to 172Er N/A N/A 1370.26 -
173Ho 172.94729(43)# 10# s ß- to 173Er 7/2-# N/A 1378.34 -
174Ho 173.95115(54)# 8# s Unknown N/A N/A 1377.1 -
175Ho 174.95405(64)# 5# s Unknown 7/2-# N/A 1385.18 -
Holmium Elemental Symbol

Recent Research & Development for Holmium

  • Holmium Laser Enucleation of the Prostate: Simulation Based Training Curriculum and Validation. 2015 Jun 27 Kuronen-Stewart C, Ahmed K, Aydin A, Cynk M, Miller P, Challacombe B, Khan MS, Dasgupta P, Aho TF, Popert R. Urology. 2015 Jun 27
  • The Impact of Increased Bladder Blood Flow on Storage Symptoms after Holmium Laser Enucleation of the Prostate. 2015 Jun 19 Saito K, Hisasue S, Ide H, Aoki H, Muto S, Yamaguchi R, Tsujimura A, Horie S. PLoS One. 2015 Jun 19
  • Holmium laser excision for urinary mesh erosion: a minimally invasive treatment with favorable long-term results. 2015 Jun 11 Ogle CA, Linder BJ, Elliott DS. Int Urogynecol J. 2015 Jun 11
  • Clinical and Pathological Characteristics of Hard Nodules Resistant to Morcellation During Holmium Laser Enucleation of the Prostate. 2015 Jun Piao S, Choo MS, Wang Y, Lee YJ, Bae J, Oh SJ. Int Neurourol J. 2015 Jun
  • Predictors of Enucleation and Morcellation Time During Holmium Laser Enucleation of the Prostate. 2015 Jul 15 Monn MF, El Tayeb M, Bhojani N, Mellon MJ, Sloan JC, Boris RS, Lingeman JE. Urology. 2015 Jul 15
  • Evaluation of 16 New Holmium:Yttrium-Aluminum-Garnet Laser Optical Fibers for Ureteroscopy. 2015 Jul 11 Akar EC, Knudsen BE. Urology. 2015 Jul 11
  • Sudden onset of a huge subcapsular renal hematoma following minimally invasive ureteroscopic holmium laser lithotripsy: A case report. 2015 Jul Zhang P, Hu WL. Exp Ther Med. 2015 Jul
  • Novel use of an optical fiber in triple-lumen catheter for percutaneous choledochoscopy and holmium: yttrium aluminum garnet laser lithotripsy of intrahepatic bile duct stones. 2015 Jul Wong JC, Lam SF, Lau JY. Gastrointest Endosc. 2015 Jul
  • Subcapsular renal hematoma after ureteroscopy with holmium:yttrium-aluminum-garnet laser lithotripsy. 2015 Jul Tao W, Cai CJ, Sun CY, Xue BX, Shan YX. Lasers Med Sci. 2015 Jul
  • Effect of Detrusor Overactivity on Functional Outcomes After Holmium Laser Enucleation of the Prostate in Patients With Benign Prostatic Obstruction. 2015 Jul Jeong J, Lee HS, Cho WJ, Jung W, You HW, Kim TH, Sung HH, Lee KS. Urology. 2015 Jul