Holmium

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dysprosium ? holmium ? erbium - ? Ho ? Es 67Ho Periodic table
Appearance
silvery white
General properties
Name, symbol, number	holmium, Ho, 67
Element category	lanthanide
Group, period, block	n/a, 6, f
Standard atomic weight	164.93032?g¡mol?1
Electron configuration	[Xe] 4f11 6s2
Electrons per shell	2, 8, 18, 29, 8, 2 (Image)
Physical properties
Phase	solid
Density (near r.t.)	8.79 g¡cm?3
Liquid density at m.p.	8.34 g¡cm?3
Melting point	1734 K,?1461 Â°C,?2662 Â°F
Boiling point	2993 K,?2720 Â°C,?4928 Â°F
Heat of fusion	17.0 kJ¡mol?1
Heat of vaporization	265 kJ¡mol?1
Specific heat capacity	(25 °C) 27.15 J¡mol?1¡K?1
Vapor pressure
P/Pa 1 10 100 1 k 10 k 100 k at T/K 1432 1584 (1775) (2040) (2410) (2964)
Atomic properties
Oxidation states	3 (basic oxide)
Electronegativity	1.23 (Pauling scale)
Ionization energies	1st: 581.0 kJ¡mol?1
	2nd: 1140 kJ¡mol?1
	3rd: 2204 kJ¡mol?1
Atomic radius	176 pm
Covalent radius	192Âą7 pm
Miscellanea
Crystal structure	hexagonal
Magnetic ordering	paramagnetic
Electrical resistivity	(r.t.) (poly) 814 n?¡m
Thermal conductivity	(300 K) 16.2 W¡m?1¡K?1
Thermal expansion	(r.t.) (poly) 11.2 ¾m/(m¡K)
Speed of sound (thin rod)	(20 °C) 2760 m/s
Young's modulus	64.8 GPa
Shear modulus	26.3 GPa
Bulk modulus	40.2 GPa
Poisson ratio	0.231
Vickers hardness	481 MPa
Brinell hardness	746 MPa
CAS registry number	7440-60-0
Most stable isotopes
Main article: Isotopes of holmium
iso NA half-life DM DE (MeV) DP 163Ho syn 4570 yr ? 0.003 163Dy 164Ho syn 29 min ? 0.987 164Dy 165Ho 100% 165Ho is stable with 98 neutrons 166Ho syn 26.763 h ?? 1.855 166Er 167Ho syn 3.1 h ?? 1.007 167Er
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Holmium (pronounced /?ho?lmi?m/, HOHL-mee-?m) is a chemical element with the symbol Ho and atomic number 67. Part of the lanthanide series, holmium is a relatively soft and malleable silvery-white metallic element, which is stable in dry air at room temperature. A rare earth metal, it is found in the minerals monazite and gadolinite. Holmium has the highest magnetic strength of any element and therefore is used for the polepieces of the strongest static magnets. Because holmium can absorb nuclear fission-bred neutrons, it is also used in nuclear control rods.

Characteristics

Physical

Ho₂O₃, left: natural light, right: fluorescent lamp light

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.

Holmium oxide has some fairly dramatic color changes depending on the lighting conditions. In daylight, it is a tannish yellow color. Under trichromatic light, it is a fiery orange red, almost indistinguishable from the way erbium oxide looks under this same lighting. This is related to the sharp emission bands of the phosphors.^[1]

A trivalent metallic rare earth element, holmium has the highest magnetic moment (10.6 Âľ_B) of any naturally-occurring element and possesses other unusual magnetic properties. When combined with yttrium, it forms highly magnetic compounds.^[2]

Chemical

Holmium metal tarnishes slowly in air and burns readily to form holmium(III) oxide:

4 Ho + 3 O₂ ? 2 Ho₂O₃

Holmium is quite electropositive and reacts slowly with cold water and quite quickly with hot water to form holmium hydroxide:

2 Ho (s) + 6 H₂O (l) ? 2 Ho(OH)₃ (aq) + 3 H₂ (g)

Holmium metal reacts with all the halogens:

2 Ho (s) + 3 F₂ (g) ? 2 HoF₃ (s) [pink]

2 Ho (s) + 3 Cl₂ (g) ? 2 HoCl₃ (s) [yellow]

2 Ho (s) + 3 Br₂ (g) ? 2 HoBr₃ (s) [yellow]

2 Ho (s) + 3 I₂ (g) ? 2 HoI₃ (s) [yellow]

Holmium dissolves readily in dilute sulphuric acid to form solutions containing the yellow Ho(III) ions, which exist as a [Ho(OH₂)₉]³⁺ complexes:^[3]

2 Ho (s) + 3 H₂SO₄ (aq) ? 2 Ho³⁺ (aq) + 3 SO2?4 (aq) + 3 H₂ (g)

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 ground-state half lives not greater than 1.117 days, and most have half lives under 3 hours. However, the metastable ^166m1Ho has a half life of around 1200 years because of its high spin. This fact, combined with a high excitation energy resulting in a particularly rich spectrum of decay gamma rays produced when the metastable state de-excites, makes this isotope useful in nuclear physics experiments as a means for calibrating energy responses and intrinsic efficiencies of gamma ray spectrometers.

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").^[4][5] Later in 1878, Per Teodor Cleve independently discovered the element while he was working on erbia earth (erbium oxide).^[6][7]

Using the method developed by Carl Gustaf Mosander, Cleve first removed all of th