Holmium

Introduction

Holmium is a chemical element with an atomic number of 67 in the periodic table. It’s not found in the Earth’s crust. Classified as a member of the lanthanide series of elements, this rare-earth metal is a divalent substance with a +3 oxidation state, strong magnetic properties, and astounding stability of its electron shell. 

Fact Box

Chemical and Physical Properties of Holmium

The symbol in the periodic table of elements: Ho

Atomic number: 67

Atomic weight (mass): 164.9 g.mol-1

Group number: 6 (Lanthanides)

Period: 6

Color: A lustrous and bright silvery metal

Physical state: Solid at room temperature

Half-life: From 6(3) milliseconds to 4,570 years

Electronegativity according to Pauling: 1.2

Density: 8.8 g.cm-3 at 20°C

Melting point: 1472°C, 2682°F, 1745 K

Boiling point: 2700°C, 4892°F, 2973 K

Van der Waals radius: Unknown

Ionic radius: Unknown

Isotopes: 36

Most characteristic isotope: 165Ho 

Electronic shell: [Xe] 4f116s2

The energy of the first ionization: 580 kJ.mol-1

The energy of the second ionization: 1136.6 kJ.mol-1

Discovery date: In 1878 by J.L. Soret 

Holmium is a rare-earth element with the periodic table symbol (Ho), atomic number 67, atomic mass of 164.9 g.mol-1, and electron configuration [Xe] 4f116s2. It comprises a lanthanoid atom and an f-block element atom. This chemical element is a soft, malleable, and lustrous metal with strong magnetic properties. It reaches its boiling point at 2700°C (4892°F, 2973 K), while the melting point is achieved at 2700°C (4892°F, 2973 K). 

A member of the lanthanide family of elements in the periodic table, holmium has an electronegativity of 1.2 according to Pauling, whereas the atomic radius according to van der Waals is unknown.  

This lanthanide is a highly reactive substance. In the form of a solution, holmium (Ho 3+) is surrounded by nine H2O molecules. Furthermore, it easily reacts with acids that dissolve this chemical and adopts the oxidation state of +3.      

How Was Holmium Discovered?

In 1978, two parallel stories on the discovery of holmium emerged.

The Discovery of the Swiss Team of Spectroscopists

Upon conducting their chemical trials by using the spectroscopy method at the University of Geneva, the Swiss chemists and spectroscopists Marc Delafontaine (1837 – 1911) and Jacques-Louis Soret (1827 – 1890) detected new lines in the spectra of the yttrium sample.

Prior to this, they had already isolated the element erbium from which they intended to extract ytterbium. Learning the fact that yttrium contains traces of other rare-earth elements, the team of Delafontaine and Soret introduced the new element ‘X’ to the world, later named as holmium (Ho). 

The Contribution of the Swedish Team of Chemists

At the same time, in 1978, a team of scientists at Uppsala, Sweden, was performing a more thorough analysis on what has been removed from ytterbium. Led by the Swedish chemist Per Teodor Cleve (1840 – 1905), the Swedish team came upon the same two new materials – the strange green and brown lines of the spectra the Swiss team had observed. Cleve applied the same method Carl Gustaf Mosander used to discover lanthanum, erbium, and terbium in his research conducted on erbia, i.e. erbium oxide sample.

The Swedish team labeled the brown chemical as ‘holmia’, while the green substance was named ‘thulia’. By conducting further analysis, the Swedish team of scientists determined that the first substance was, in fact, holmium oxide, while the second one was thulium oxide. 

In the end, it remains unclear whether any of the research teams succeeded in isolating the pure elemental form of holmium back in 1978 since the rare-earth element dysprosium was later extracted from holmium. 

How Did Holmium Get Its Name?

Holmium got its name after Holmia, the Latin name for Stockholm, Sweden.

Where Can You Find Holmium?

As is the case with all rare-earth metals, holmium does not occur naturally in its free elemental form. It’s mined from the minerals gadolinite, monazite, and bastnäsite. These mineral ores are the main sources of this soft metal silvery substance with a lustrous shine. 

Typically, the monazite and bastnaesite ores are first processed to extract yttrium, after which holmium is isolated via the ion-exchange process. In the laboratory, the pure holmium substance is obtained by reacting calcium metal with holmium fluoride (HoF3). 

The United States, China, Sri Lanka, Brazil, India, and Australia are the countries where the largest holmium ore mines are located. 

Holmium in Everyday Life

Being a rare-earth element, holmium has very limited use in everyday life. Its unusual magnetic properties make holmium most suitable in the following instances:

  • As an addition in alloys that are further applied in the manufacturing of magnets. Also, this lanthanide has found its use as a flux concentrator for high magnetic fields; 
  • Furthermore, holmium possesses a strong ability to absorb neutrons. Due to this chemical property, element 67 is used in nuclear reactors in order to keep the chain reaction under control; 
  • As a calibrator, Ho is the preferred chemical in the manufacturing process of optical spectrophotometers. Moreover, holmia or holmium(III) oxide (Ho2O3) gives yellow or red color to cubic zirconia or glass; 
  • Finally, the radioactive isotopes of holmium have a significant application in the solid-state lasers used for vaporizing tumorous tissues during non-invasive medical procedures for the treatment of cancer and kidney stones. 

How Dangerous Is Holmium?

Holmium is considered to be of low toxicity. Since this element is found in minuscule traces in the human body, it’s considered to have a stimulating effect on the metabolic processes in the body by affecting the mechanisms of some bacteria. However, these claims are yet to be thoroughly studied. 

Environmental Effects of Holmium

There are no known hazards imposed by the presence of the elemental form of holmium in the environment. 

Isotopes of Holmium

There are 36 forms of holmium. The isolated holmium isotopes have atomic masses that range from 140Ho to 175Ho. However, the pure elemental form of holmium is made up of only one form of the element, i.e. the stable isotope 165Ho. 

Among the synthetic radioactive isotopes of holmium, holmium-163 is the most stable radioactive form of this rare earth element, with a half-life of 4570 years. 

Nuclide

[n 1]

 Z N Isotopic mass (Da)

[n 2][n 3]

 Half-life

[n 4]

 Decay

mode

[n 5]

 Daughter

isotope

[n 6]

 Spin and

parity

[n 7][n 4]

 Natural abundance (mole fraction)
Excitation energy[n 4] Normal proportion Range of variation
140Ho 67 73 139.96854(54)# 6(3) ms 8+#
141Ho 67 74 140.96310(54)# 4.1(3) ms (7/2−)
142Ho 67 75 141.95977(54)# 400(100) ms β+ 142Dy (6 to 9)
p 141Dy
143Ho 67 76 142.95461(43)# 300# ms

[>200 ns]

 β+ 143Dy 11/2−#
144Ho 67 77 143.95148(32)# 0.7(1) s β+ 144Dy
β+, p 143Tb
145Ho 67 78 144.94720(32)# 2.4(1) s β+ 145Dy (11/2−)
146Ho 67 79 145.94464(21)# 3.6(3) s β+ 146Dy (10+)
β+, p (rare) 145Tb
147Ho 67 80 146.94006(3) 5.8(4) s β+ 147Dy (11/2−)
β+, p (rare) 146Tb
148Ho 67 81 147.93772(14) 2.2(11) s β+ 148Dy (1+)
149Ho 67 82 148.933775(20) 21.1(2) s β+ 149Dy (11/2−)
150Ho 67 83 149.933496(15) 76.8(18) s β+ 150Dy 2−
151Ho 67 84 150.931688(13) 35.2(1) s β+ (78%) 151Dy 11/2(−)
α (22%) 147Tb
152Ho 67 85 151.931714(15) 161.8(3) s β+ (88%) 152Dy 2−
α (12%) 148Tb
153Ho 67 86 152.930199(6) 2.01(3) min β+ (99.94%) 153Dy 11/2−
α (.05%) 149Tb
154Ho 67 87 153.930602(9) 11.76(19) min β+ (99.98%) 154Dy 2−
α (.02%) 150Tb
155Ho 67 88 154.929103(19) 48(1) min β+ 155Dy 5/2+
156Ho 67 89 155.92984(5) 56(1) min β+ 156Dy 4−
157Ho 67 90 156.928256(26) 12.6(2) min β+ 157Dy 7/2−
158Ho 67 91 157.928941(29) 11.3(4) min β+ (93%) 158Dy 5+
α (7%) 154Tb
159Ho 67 92 158.927712(4) 33.05(11) min β+ 159Dy 7/2−
160Ho 67 93 159.928729(16) 25.6(3) min β+ 160Dy 5+
161Ho 67 94 160.927855(3) 2.48(5) h EC 161Dy 7/2−
162Ho 67 95 161.929096(4) 15.0(10) min β+ 162Dy 1+
163Ho 67 96 162.9287339(27) 4570(25) y EC 163Dy 7/2−
164Ho 67 97 163.9302335(30) 29(1) min EC (60%) 164Dy 1+
β− (40%) 164Er
165Ho 67 98 164.9303221(27) Observationally Stable[n 8] 7/2− 1.0000
166Ho 67 99 165.9322842(27) 26.83(2) h β− 166Er 0−
167Ho 67 100 166.933133(6) 3.003(18) h β− 167Er 7/2−
168Ho 67 101 167.93552(3) 2.99(7) min β− 168Er 3+
169Ho 67 102 168.936872(22) 4.72(10) min β− 169Er 7/2−
170Ho 67 103 169.93962(5) 2.76(5) min β− 170Er 6+#
171Ho 67 104 170.94147(64) 53(2) s β− 171Er 7/2−#
172Ho 67 105 171.94482(43)# 25(3) s β− 172Er
173Ho 67 106 172.94729(43)# 10# s β− 173Er 7/2−#
174Ho 67 107 173.95115(54)# 8# s
175Ho 67 108 174.95405(64)# 5# s 7/2−#

Source: Wikipedia

List of Holmium Compounds 

Holmium’s molecule is stable when exposed to dry air. Its most commonly occurring oxidation state is +3. When exposed to high temperatures or moist air, holmium oxidizes to a yellow oxide (Ho2O3). 

The most frequently occurring compounds of holmium are presented in the following list:

  • Holmium titanate
  • Holmium(III) bromide
  • Holmium chloride
  • Holmium(III) chloride
  • Holmium(III) fluoride
  • Holmium(III) oxide
  • Holmium silicide
  • Holmium iodide
  • Holmium nitride
  • Holmium vanadate

5 Interesting Facts and Explanations

  1. For a member of the lanthanide family of elements, holmium is pretty rare. It’s the 56th most abundant element in the Earth’s crust. However, despite being labeled as rare, holmium is 20 times more abundant than silver. 
  2. Holmium does not exist at all in the Earth’s atmosphere. 
  3. Among all of the naturally occurring elements, holmium possesses the highest magnetic moment (10.6 µB). 
  4. Most of the chemical compounds that contain holmium display brownish-yellow color. 
  5. Holmium(III) oxide (Ho2O3) is characterized with the strongest paramagnetic properties among all known chemical substances.