Holmium was discovered in 1878. It has highest magnetic moment that is why it is used to create strongest known magnetic field by placing it as magnetic flux concentrator. It has fluorescent properties and is used in laser and glass colorant applications.
History and Discovery
Holmium was discovered in 1878 by Jacques-Louis Soret and Marc Delafontaine. They observed the aberrant spectrographic absorption bands of unknown element. They called that element ‘’X’’. Per Teodar Cleve discovered erbium oxide in the same year. He removed all the impurities and formed two material one is brown in color other one is in green. He named green one thulia later he called it thulium oxide and called brown one holmia later which was found to be holmium oxide. Through fractional precipitation holmium was isolated by Paul Lecoq de Boisbaudran in 1886. But in pure metal form it was isolated by Otto Holmberg in 1911. The name Holmium derived from Greek word ‘Holmia’ which means ‘Stockholm’ [1].
Holmium
| Periodic Table Classification | Group n/a Period 6 |
|---|---|
| State at 20C | Solid |
| Color | Silvery white |
| Electron Configuration | [Xe] 4f11 6s2 |
| Electron Number | 67 |
| Proton Number | 67 |
| Electron Shell | 2, 8, 18, 29, 8, 2 |
| Density | 8.80 g.cm-3 at 20°C |
| Atomic number | 67 |
| Atomic Mass | 164.93 g.mol -1 |
| Electronegativity according to Pauling | 1.23 |
Occurrence
Holmium is not free in nature. It is present in combined form and the common minerals of holmium include gadolinite (silicate mineral), monazite (reddish brown phosphate mineral) and other rare earth minerals. Holmium is about 1.4 part per million in the Earth crust. It is about 56th most abundant element. It makes 1 part per million of the soil, 400 parts per quadrillion of seawater, 500 parts per million of the universe by mass. Holmium main deposits are found in China, United States, Brazil, India, Sri Lanka and Australia. Holmium is extracted commercially through ion exchange method from monazite sand.
Physical Characteristics
Holmium is a bright silver lustrous metal. It is soft and corrosion resistant element. At standard temperature and pressure, it is stable in dry air. It oxidizes quickly in moist air and high temperature to form yellowish oxide. In its oxides form, its color changes take place dramatically due to its sharp absorption characteristics as it tarnished yellow to fiery orange red. It is paramagnetic at ambient temperature and ferromagnetic below 19 K. Holmium chemical symbol is Ho with atomic number 67. Its atomic weight is 164.93. Holmium melting point is 1461OC and boiling point is 2600OC. Its density at room temperature is about 8.79 g/cm3 [2].
Chemical Characteristics
Holmium is a reactive metal. It is tarnished slowly in the air. It burns quickly and form holmium oxide. It is electropositive and trivalent. It reacts slowly with cold water and quickly with hot water to form holmium hydroxide. Holmium also react with all halogens to form HoF3 (Pink), HoCl3 (yellow), HoBr3 (yellow) and HoI3 (yellow). It dissolves easily in dilute sulfuric acid and form solution, which contain yellow Ho (lll) ions. It is mostly exist in +3 oxidation state. It dissolves in acids too [3].
Significance and Uses
- Holmium is used to create artificial magnetic field because it has highest magnetic strength.
- It is used in burnable poison to regulate nuclear reactor.
- It is also find in YIG (yttrium-iron-garnet) and YLF (yttrium-lanthanum-fluoride) solid state laser which are found in microwave equipment.
- Holmium is also useful in medical, dental and fiber-optical applications.
- It is also used as colorant in cubic zirconia (cubic crystalline form of zirconium dioxide) and glass giving yellow or red color.
- Glass which contain holmium oxide and holmium oxide solution have sharp optical absorption, its spectral range lies 200-900 nm.
- It is also used in optical spectrophotometers calibration standard.
- 166m1Ho is used in calibration of gamma rays’ spectrometers.
- In oxide form it is used as yellow gas coloring.
- Holmium is also used in nuclear reactors for nuclear control rods.
- Holmium is also used in treating cancers and kidney stones.
Health Effects
Holmium is considered least abundant element in human body. It has no biological role. But some studies investigate that it stimulates metabolism.
Isotopes of Holmium
Holmium naturally contains one stable isotope Ho-165. It has 30 isotopes with mass number 141 to 172. It has some synthetic radioisotopes in which the most stable is Ho-163 with the half-life of 4570 years. Other radioisotope have half-lives at ground state not greater than 1.117 days and most have under 3 hours. But the metastable 166m1Ho has 1200 years half-life due to its high spin.
REFERENCES
[1]. https://www.chemicool.com/elements/holmium.html
[2]. https://en.wikipedia.org/wiki/Holmium
[3]. Emsley, John (2011). Nature’s Building Blocks