An Overview about the Chemical Element Holmium


Symbol: Ho

Atomic Number: 67

Atomic Mass: 164.93031 amu (atomic mass units)

Melting Point: 1470.0 C (1743.15 K, 2678.0 F)

Boiling Point: 2720.0 C (2993.15 K, 4928.0 F)

Number of Protons: 67

Number of Electrons: 67

Number of Neutrons: 98

Classification: Rare Earth

Crystal Structure: Hexagonal

Density @ 20 C (293 K, 68 F): 8.54 grams per cubic centimeter

Color: Silver

The first indications of the existence of holmium came in 1878 when the two Swiss chemists J. L. Soret and M. Delafontaine noticed its distinctive absorption spectrum. They announced their discovery as “Element X”.

In 1879 the Swedish chemist Per Theodor Cleve was using methods developed by Carl Gustaf Mosander to look for impurities in oxides of rare earth elements. Mosander had discovered the elements lanthanum, erbium and terbium using such methodologies. Cleve was using these methods on an oxide of the element erbium known as erbia. From this impure oxide Cleve found two new rare earth oxides one green and the other brown. The green one he called thulia and the brown one holmia. These were the oxides of the elements thulium and holmium. Holmium derives its name from the Latin name for Stockholm “Holmia” which was Cleve’s home city.

Holmium is a member of the lanthanide or lanthanoid series of rare earth elements. It is stable at room temperature providing the air is dry. At raised temperatures or in moist air holmium will rapidly oxidize. It is a soft and malleable metal. The element has some unusual magnetic properties which require further investigation.

There is only one naturally occurring isotope of holmium. This isotope is holmium-165 and it is stable. A number of unstable isotopes of the element have been produced with mass numbers ranging from 140 to 175. Isotope holmium-141m has the shortest half-life at 6.6 microseconds and holmium-166m the longest at 1200 years.

Holmium is found along with a number of other rare earth elements in a number of mineral ores such as gadolinite. Within monazite sand it can be found at about 0.05% and it is from this source it is commercially extracted. This extraction must be carried out with caution as monazite also contains the highly radioactive element thorium. Pure holmium is produced by reduction of either holmium fluoride or holmium chloride in their anhydrous states using calcium metal.

At present there are no commercial applications for the element holmium. It is possible that its magnetic properties may prove useful in the future.