Description

Basic Information

Element Name: Holmium
Symbol: Ho
Atomic Number: 67
Atomic Weight: 164.93
Element Category: Lanthanide (Rare Earth Element)
Standard State: Solid
Appearance: Silvery-white, soft, and malleable metal

Chemical and Physical Properties

Density: 8.80 g/cm³
Melting Point: 1,474 °C (2,685 °F)
Boiling Point: 2,700 °C (4,892 °F)
Electronegativity (Pauling scale): 1.23
Oxidation State: +3 (dominant)
Magnetism: Strongly paramagnetic; exhibits the highest magnetic moment of any naturally occurring element (10.6 μB per atom)

Reactivity and Storage

Holmium oxidizes slowly in dry air but rapidly in moist conditions, forming a yellow oxide layer. It reacts with water and dissolves in acids. For long-term storage, holmium metal should be sealed under inert gas or mineral oil to prevent oxidation.

Occurrence and Extraction

Holmium is not found in pure form in nature but is present in rare earth minerals like monazite and xenotime. It is obtained through standard rare earth separation techniques such as solvent extraction and ion-exchange.

Isotopes

Naturally occurring holmium consists entirely of one stable isotope: Ho-165
Several radioactive isotopes have been synthesized for research

Key Applications

1. Magnets and Magnetic Materials

Holmium’s extremely high magnetic moment makes it valuable in high-strength magnets and magnetic flux concentrators
Used in:
- MRI shielding
- Cryogenic magnetic applications
- Magnetic calibration materials

2. Nuclear Control Systems

Due to its high neutron-absorption cross-section, holmium is used in nuclear reactor control rods to help regulate fission reactions

3. Laser Technology (Ho:YAG Lasers)

Holmium-doped yttrium aluminum garnet (Ho:YAG) lasers emit at 2.1 μm
Extensively used in:
- Urological surgeries (e.g., kidney stone fragmentation)
- Orthopedics
- ENT and spinal surgery
Benefits include shallow penetration and precise ablation with minimal thermal damage

4. Glass and Crystal Coloring

Holmium oxide imparts yellow-red coloring to glass and is used in specialized optical filters
Also serves as a standard in spectrophotometer calibration due to its sharp absorption bands

5. Data Storage Alloys

Holmium is used in magnetic-optical materials and rare earth cobalt alloys for high-density data storage (e.g., in Blu-ray and magneto-optic disks)

Interesting Facts

Discovered in 1878 by Swiss chemist Marc Delafontaine and independently by Per Teodor Cleve
Named after Stockholm, Sweden (Latin: Holmia)
Exhibits one of the highest magnetic susceptibilities of all elements
Despite being relatively rare, it is commercially available due to improved rare earth separation methods