Lanthanum was discovered in 1838. It is the most reactive member of the lanthanide series and have various industrial applications.
History and Discovery
Lanthanum was discovered in the 19th century, this came precisely in 1838 by a Swedish chemist known as Carl Mustav Gosander at the Karolinska Institute in Stockholm. It was isolated as an impurity from cerium nitrate. Pure or elemental form of lanthanum was obtained in 1923 [1]. The name lanthanum was given to the newly discovered metal, which was derived from the Greek word lanthanein, that means hidden. The symbol of lanthanum is La.
Lanthanum
| Periodic Table Classification | Group 3 Period 6 |
|---|---|
| State at 20C | Solid |
| Color | Silvery white |
| Electron Configuration | [Xe] 5d1 6s2 |
| Electron Number | 57 |
| Proton Number | 57 |
| Electron Shell | 2, 8, 18, 18, 9, 2 |
| Density | 6.15 g.cm-3 at 20°C |
| Atomic number | 57 |
| Atomic Mass | 138.91 g.mol -1 |
| Electronegativity according to Pauling | 1.10 |
Occurrence
Lanthanum is not a rare metal. It is ranked as the twenty-eighth most abundant metal in the earth’s crust and is thrice (39 mg/kg of the earth’s crust) as abundant as lead. In nature, lanthanum mostly exists in combination with cerium. The most common mineral so lanthanum includes bastnaesite and monazite [2].
Physical Characteristics
Lanthanum is a whitish silver metal. It is malleable and soft and can be cut with a knife. It is the first member of the lanthanide series of the periodic table, that is comprised of fifteen similar elements. Lanthanum is also the first member of the transition metals of the 6th period. At room temperature, lanthanum is present in the configuration of the hexagonal structure, and as the temperature is increased from 310C to 865 it changes from a face-centred cube structure to a body-centred cubic configuration. The melting point has been approximated to be 920°C and boiling point is 3464 °C [3]. At 20 degree Celsius, its density is known to be 6.16 g/cm3. Lanthanum has the lowest volatility among the elements of the lanthanide series.
Chemical Characteristics
Lanthanum is a chemically reactive metal and is the most reactive element in the lanthanide series. It readily oxides when exposed to air to form an oxide and is slowly tarnished to lose its silvery appearance. It rapidly burns to from lanthanum oxide in air. Lanthanum reacts with sulfur, selenium, boron, phosphorus, nitrogen and sometimes silicon. It reacts with halogens to form trihalides. It also reacts with water to form lanthanum hydroxide. Lanthanum also dissolves in dilute sulfuric acid. The most common and stable oxidation state of lanthanum in compounds is +3.
Significance and Uses
- Lanthanum has proved to be very useful in the photography industry. It is useful in optics, helping the flexibility of the refractive index of cameras and video cameras as well as in the modification of the structure of the glass crystals.
- Lanthanum is useful in the reducing of the intensity and harmfulness of the X-rays radiations and lasers as well as other lights that have high penetrating capabilities which cause damage to human tissues and organs.
- Lanthanum is useful for power generators and is widely used to make batteries and fuel cells.
- Lanthanum is used in projectors and studio lights.
- Lanthanum alloys are used to produces sparks that are powerful enough to light a cigarette and for this reason, it has been found to be useful in the production of cigarette lighters.
- Various compounds of lanthanum are also responsible for bringing forth the bright white light seen in carbon arc lamps.
- Optical fiber production is one of the most recently discovered usefulness of lanthanum. Optical fiber is useful in the digital world for efficient data transfer.
- Lanthanum is used medically for the treatment of hypophosphatemia. This is important in treating patients who have kidney injuries and diseases such as acute kidney injury and chronic kidney disease.
Health Effects
This element is not a very toxic metal. It does not have any biological importance for humans. It has antimicrobial activity and can be hazardous to microbes. Care should be taken while handling lanthanum, as injection of lanthanum can lead to damage to organs including spleen, liver and heart.
Isotopes of Lanthanum
Naturally occurring lanthanum have two isotopes, one stable isotope, lanthanum-139, and one radioactive isotope that has a very long half-life, lanthanum-138. Lanthanum-139 the most abundant of the lanthanum isotopes. There are 38 known radioisotopes that have been discovered. Lanthanium-138 is very rare and is believed to belong to the primordial period as it has a half-life of 1.02x 1011 years. Two other isotopes, lanthanum-140 and lanthanum-137 have half-lives of 1.6781 days and 60,000 years, respectively. Most of the other radioisotopes of these elements do not have half-lives of more than a minute.
REFERENCES
[1]. Patnaik, Pradyot (2003). Handbook of Inorganic Chemical Compounds. McGraw-Hill. pp. 444–446. ISBN 0-07-049439-8. Retrieved 2009-06-06.
[2]. “Monazite-(Ce) Mineral Data”. Webmineral. Retrieved 10 July 2016
[3]. Krishnamurthy, Nagaiyar and Gupta, Chiranjib Kumar (2004) Extractive Metallurgy of Rare Earths, CRC Press, ISBN 0-415-33340-7