67
  Ho  
164.930320
Holmium

Name: Holmium
Symbol: Ho
Atomic Number: 67
Atomic Weight: 164.930320
Family: Rare Earth Elements
CAS RN: 7440-60-0
Description: A silvery white soft and malleable rare earth metal
State (25C): Solid
Oxidation states: +3

Molar Volume: 18.74 cm3/mole
Valence Electrons: 4f116s2

Boiling Point:  2968K, 2695C, 4883F
Melting Point:
1743K, 1470C, 2678F
Electrons Energy Level: 2, 8, 18, 29, 8, 2
Isotopes: 35 + 1 Stable + 21 meta states
Heat of Vaporization:  241 kJ/mol
Heat of Fusion: 12.2 kJ/mol
Density:  8.8g/cm3 @ 300K
Specific Heat:  0.16 J/gK
Atomic Radius: 2.47
Ionic Radius: 0.901
Electronegativity: 1.23 (Pauling); 1.1 (Allrod Rochow)
57
La
138.9
58
Ce
140.1
59
Pr
140.9
60
Nd
144.2
61
Pm
(145)
62
Sm
150.4
63
Eu
152.0
64
Gd
157.3
65
Tb
158.9
66
Dy
162.5
67
Ho
164.9
68
Er
167.3
69
Tm
168.9
70
Yb
173.0
71
Lu
175.0

1s2 2s2p6 3s2p6d10 4s2p6d10f11 5s2p6 6s2

History

Holmium (Holmia, Latin name for Stockholm) was discovered by Marc Delafontaine and Jacques-Louis Soret in 1878 who noticed the aberrant spectrographic absorption bands of the then-unknown element (they called it "Element X").  Later in 1879, Per Teodor Cleve, a Swedish chemist, independently discovered the element while he was working on erbia earth (erbium oxide).

Using the method developed by Carl Gustaf Mosander to discover lanthanum, erbium and terbium, Cleve looked for impurities in the oxides of other rare earth element.    He started with erbia, the oxide of erbium (Er2O3), and removed all of the known contaminants.  The result of that effort was two new materials, one brown and one green.   He named the brown substance holmia (after the Latinized name for Cleve's home town, Stockholm) and the green one thulia.  Holmia is the oxide of the element holmium and thulia is the oxide of the element thulium.  Holmium's absorption spectrum was observed earlier that year by J. L. Soret and M. Delafontaine, Swiss chemists.

Characteristics

Like most of the rare-earth metals, holmium is a relatively soft and malleable element that is fairly corrosion-resistant and stable in dry air at standard temperature and pressure.  In moist air and at higher temperatures, however, it quickly oxidizes; forming a yellowish oxide.  In pure form, holmium possesses a metallic, bright silvery luster.

1s2
2s2 2p6
3s2 3p6 3d10
4s2 4p6 4d10 4f11
5s2 5p6
6s2

Like most of the other rare-earth metals, it is silvery and soft, and can be pounded or rolled into very thin sheets. At normal temperatures it is fairly inert but will oxidize at high temperatures and humidities.

Holmium is generally obtained from monazite sand, where it is present to the extent of about 0.05%. Most holmium use is confined to research.

A trivalent metallic rare earth element, holmium has the highest magnetic moment (10.6B) of any naturally-occurring element and possesses other unusual magnetic properties.  When combined with yttrium, it forms highly magnetic compounds.

Occurrence

Like all other rare earths, holmium is not naturally found as a free element. It does occur combined with other elements in the minerals gadolinite, monazite, and in other rare-earth minerals.  It is commercially extracted via ion-exchange from monazite sand (0.05% holmium) but is still difficult to separate from other rare earths. The element has been isolated through the reduction of its anhydrous chloride or fluoride with metallic calcium.  Its estimated abundance in the Earth's crust is 1.3 milligrams per kilogram.

Applications

Because of its magnetic properties, holmium has been used to create the strongest artificially-generated magnetic fields when placed within high-strength magnets as a magnetic pole piece (also called a magnetic flux concentrator).  Since it can absorb nuclear fission -bred neutrons, the element is also used in nuclear control rods.   Other commercial applications of the element include;

Few other uses have been identified for this element.

Compounds

Holmium forms no commercially important compounds. Some of holmium's compounds include: holmium oxide (Ho2O3), holmium fluoride (HoF3) and holmium iodide (HoI3).

Isotopes

Natural holmium contains one stable isotope, holmium-165.  Some synthetic radioactive isotopes are known, the most stable one is holmium 163, with a half life of 4570 years.  All other radioisotopes have half lives not greater than 1.117 days, and most have half lives under 3 hours.

atom.gif (700 bytes)

Isotope  
Atomic Mass
 
Half-Life
140Ho 139.96854 6 ms
141Ho 140.96310 4.1 ms
142Ho 141.95977 400 ms
143Ho 142.95461 ~300 ms
144Ho 143.95148 0.7 seconds
145Ho 144.94720 2.4 seconds
146Ho 145.94464 3.6 seconds
147Ho 146.94006 5.8 seconds
148Ho 147.93772 2.2 seconds
148m1Ho   9.49 seconds
149Ho 148.933775 21.1 seconds
149m1Ho   56 seconds
150Ho 149.933496 76.8 seconds
150m1Ho   23.3 seconds
151Ho 150.931688 35.2 seconds
151mHo   47.2 seconds
152Ho 151.931714 161.8 seconds
152m1Ho   50.0 seconds
153Ho 152.930199 2.01 minutes
153m1Ho   9.3 minutes
154Ho 153.930602 11.76 minutes
154mHo   3.10 minutes
155Ho 154.929103 48 minutes
156Ho 155.92984 56 minutes
156m1Ho   7.8 minutes
156m2Ho   9.5 seconds
157Ho 156.928256 12.6 minutes
158Ho 157.928941 11.3 minutes
158m1Ho   28 minutes
158m2Ho   21.3 minutes
159Ho 158.927712 33.05 minutes
159mHo   8.30 seconds
160Ho 159.928729 25.6 minutes
160m1Ho   5.02 hours
160m2Ho   3 seconds
161Ho 160.927855 2.48 hours
161mHo   6.76 seconds
162Ho 161.929096 15.0 minutes
162mHo   67.0 minutes
163Ho 162.9287339 4570 years
163mHo   1.09 seconds
164Ho 163.9302335 29 minutes
164mHo   38.0 minutes
165Ho 164.9303221 Stable
166Ho 165.9322842 26.83 hours
166m1Ho   1.20 x 103 years
167Ho 166.933133 3.003 hours
168Ho 167.93552 2.99 minutes
168m1Ho   132 seconds
169Ho 168.936872 4.72 minutes
170Ho 169.93962 2.76 minutes
170mHo   43 seconds
171Ho 170.94147 53 seconds
172Ho 171.94482 25 seconds
173Ho 172.94729 ~10 seconds
174Ho 173.95115 ~8 seconds
175Ho 174.95405 ~5 seconds

Precautions

The element, as with other rare earths, appears to have a low acute toxic rating.   Holmium plays no biological role in humans but may be able to stimulate metabolism.

atom.gif (700 bytes)

Holmium Data

 

Atomic Structure

Atomic Radius (): 2.47
Atomic Volume cm3/mol : 18.7cm3/mol
Covalent Radius: 1.58
Crystal Structure: Hexagonal
Ionic Radius: 0.901

Chemical Properties

Electrochemical Equivalents: 2.0512g/amp-hr
Electron Work Function: unknown
Electronegativity: 1.23 (Pauling); 1.1 (Allrod Rochow)
Heat of Fusion: 12.2kJ/mol
First Ionization Potential: 6.018
Second Ionization Potential: 11.805
Third Ionization Potential: 22.843
Valence Electron Potential (-eV): 47.9
Ionization Energy (eV): 6.022 eV

Physical Properties

Atomic Mass Average: 164.9303
Boiling Point: 2968K, 2695C, 4883F
Melting Point: 1743K, 1470C, 2678F
Heat of Vaporization: 241 kJ/mol
Coefficient of Lineal Thermal Expansion/K-1: 9.5E-6
Electrical Conductivity: 0.0124 106/cm
Thermal Conductivity: 0.162 W/cmK
Density: 8.8g/cm3 @ 300K
Enthalpy of Atomization: 301 kJ/mole @ 25C
Enthalpy of Fusion: 11.76 kJ/mole
Enthalpy of Vaporization: 241 kJ/mole
Molar Volume: 18.74 cm3/mole
Specific Heat: 0.16 J/gK
Vapor Pressure: unknown
Estimated Crustal Abundance: 1.3 milligrams per kilogram
Estimated Oceanic Abundance: 2.210-7 milligrams per liter