Lanthanides Facts (Lanthanoids)


Lanthanide Series (Lanthanoids)
The lanthanides or lanthanoids are elements 57 (lanthanum) to element 71 (lutetium).

The lanthanides are a series of periodic table elements including elements 57 to 71 (lanthanum to lutetium). Chemists refer to these 15 elements using the symbol Ln. They are called “lanthanides” because they share properties in common with lanthanum.

Here is a list of the lanthanides, a look at their common properties, their uses, and other facts.

Lanthanide Location

The lanthanides are located on the top row of the two rows of elements found below the main body of the periodic table. Placing the lanthanides and the actinides (the row below the lanthanides) below the other elements is just a matter of aesthetics. The lanthanides belong to period 6, like cesium, barium, and hafnium. Essentially, they are a special class of transition metals.

List of the Lanthanides

The lanthanide series includes the following 15 elements:

Atomic NumberSymbolNameAtomic Mass
57LaLanthanum138.91
58CeCerium140.12
59PrPraseodymium140.91
60NdNeodymium144.24
61PmPromethium[145]
62SmSamarium150.36
63EuEuropium151.96
64GdGadolinium157.25
65TbTerbium158.93
66DyDysprosium162.50
67HoHolmium164.93
68ErErbium167.26
69TmThulium168.93
70YbYtterbium173.05
71LuLutetium174.97

Properties of the Lanthanides

The lanthanides share several common properties:

  • The lanthanides (and actinides) are f-block elements or inner transition metals. What this means is that atoms of these elements have one of more electrons in an inner f-orbital. Some sources consider lanthanum to be a d-block element, while others include it as an f-block element because it starts the series (even though its f-orbital is empty).
  • All of the lanthanide elements are silver-colored, reactive solid metals that tarnish in air.
  • The metals are relatively soft, with hardness increasing with atomic number.
  • The lanthanides have high melting and boiling points.
  • The lanthanides display multiple oxidation states. The +3 state is the most stable, but the +2 and +4 oxidation states are also common.
  • Moving from left to right across the table (increasing atomic number), the radium of successive 3+ lanthanide ions decreases rather than increases. This phenomenon is called “lanthanide contraction.”
  • The elements react with water, liberating hydrogen gas. The reaction proceeds more quickly at higher temperature.
  • The lanthanides reaction with H+ (dilute acid) to release H2. This reaction proceeds rapidly at room temperature.
  • The elements react exothermically with hydrogen gas.
  • The lanthanides are strong reducing agents.
  • Many lanthanide burn in air.
  • Most lanthanide compounds are ionic and paramagnetic.
  • Many lanthanide compounds fluoresce under ultraviolet light.
  • Like the transition metals, the lanthanides form colored complexes. However, the colors tend to be pale or pastel, due to weak forbidden f x f optical transitions.
  • The lanthanides have high coordination numbers. They are greater than 6, usually 8 or 9, but may be as high as 12. The coordination numbers decrease moving across the series.

Lanthanide Uses

The lanthanides are not especially rare elements (despite being rare earths), but they are difficult to separate from one another from their ores. They are used in relatively small amounts compared to other elements, but have many uses. Most lanthanide compounds are used to make glass and catalysts. They are used to make magnets, superconductors, phosphors, lasers, and luminescent materials. Lanthanide oxides form high-temperature alloys when combined with tungsten and other metals. The addition of <1% Mischmetall (50% Ce, 25% La, 25% other light lanthanides) or lanthanide silicides improves the strength and workability of low alloy steel. In the life sciences, lanthanide complexes are important fluorophores and may act as anticancer agents. The lanthanides serve no known biological role in humans. The non-radioactive elements exhibit low toxicity.

Sources

Each lanthanide mineral potentially contains all the elements in the series. The three main ores are monazite, xenotime, and euxenite. Monazite is rich in lighter lanthanides. Xenotime is rich in heavier lanthanides. Euxenite contains a fairly even mix of lanthanides.

Lanthanide vs Lanthanoid

The IUPAC actually prefers the name “lanthanoid” to “lanthanide” because the -ide suffix indicates a negative ion. The -oid suffix is consistent with the naming of another element group — the metalloids. However, scientists and peer-reviewed articles still use the terms “lanthanides” or “lanthanide series.”

Lanthanides vs Rare Earths

Sometimes the lanthanides are called the rare earth elements or simply “rare earths.” While the rare earth elements do include all of the lanthanides, they also include scandium and yttrium.

References

  • Atwood, David A. (ed.) (2013). The Rare Earth Elements: Fundamentals and Applications. John Wiley & Sons. ISBN 9781118632635.
  • Gray, Theodore (2009). The Elements: A Visual Exploration of Every Known Atom in the Universe. New York: Black Dog & Leventhal Publishers. ISBN 978-1-57912-814-2.
  • Holden, Norman E.; Coplen, Tyler (2004). “The Periodic Table of the Elements”. Chemistry International. IUPAC. 26 (1): 8. doi:10.1515/ci.2004.26.1.8
  • Krishnamurthy, Nagaiyar and Gupta, Chiranjib Kumar (2004). Extractive Metallurgy of Rare Earths. CRC Press. ISBN 0-415-33340-7
  • McGill, Ian (2005) “Rare Earth Elements” in Ullmann’s Encyclopedia of Industrial Chemistry. Wiley-VCH, Weinheim. doi:10.1002/14356007.a22_607