The d and f - block Elements

The Lanthanide

What according to you are the number of elements present in and around us? They are countable, but difficult to count them on fingers as there are 118 of them. Among these are certain hidden elements (in the periodic table) like the lanthanides that cannot be ignored. Let us see the lanthanide elements are in detail.

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Lanthanides

Lanthanoids, also called lanthanides are 15 consecutive chemical elements in the periodic table from lanthanum to lutetium (atomic numbers 57–71). With scandium and yttrium, they make up the rare-earth metals. Their atoms have similar configurations and similar physical and chemical behaviour; the most common valencies are 3.

Lanthanide

(Source: Wikimedia)

As the elements in the series are chemically similar to lanthanum, they are termed as lanthanoids. Even though these elements are called lanthanides, the International Union of Pure and Applied Chemistry [IUPAC], the international body in charge of chemical nomenclature, prefers the term lanthanoid, since the ‘-ide’ending is usually reserved for negatively charged ions.

Location in the Periodic Table

In the periodic table, two additional rows below the main body of the table as parts of the table’s sixth and seventh row (periods) are the lanthanides and the actinides.

Elements

The fifteen lanthanide elements start from Lanthanum (La) and further go with Cerium (Ce), Praseodymium (Pr), Neodymium (Nd), Promethium (Pm), Samarium (Sm), Europium (Eu), Gadolinium (Gd), Terbium (Tb), Dysprosium (Dy), Holmium (Ho), Erbium (Er), Thulium (Tm), Ytterbium (Yb), and finally Lutetium (Lu).

Characteristics

  • The lanthanide metals are soft; their hardness increases across the series.
  • Resistivity of the lanthanide metals is relatively high, ranging from 29 to 134 μOhm·cm.
  • The lanthanides are strongly paramagnetic. Gadolinium becomes ferromagnetic at below 16°C (Curie point). The other heavier lanthanides – terbium, dysprosium, holmium, erbium, thulium, and ytterbium – become ferromagnetic at much lower temperatures.
  • Compared to most other nondietary elements, non-radioactive lanthanides are classified as having low toxicity.
  • The lanthanides obey the Oddo-Harkins rule – odd-numbered elements are less abundant than their even-numbered neighbours.

Oxidation States

All lanthanide elements commonly have the +3 oxidation state. All of the lanthanides can form +2 complexes in solution.

Applications

  • Nearly 15,000 tons/year of lanthanides is consumed as catalysts to produce glasses. These 15,000 tons correspond to about 85% of the lanthanide production.
  • The optoelectronics applications use lanthanide ions as active ions in luminescent materials. The most notable application is the Nd: YAG laser. Erbium-doped fibre amplifiers are significant devices in optical-fibre communication systems. The television sets contain phosphors with lanthanide dopants. The earliest colour television CRTs had a poor-quality red; europium as a phosphor dopant made good red phosphors possible.
  • TIG welding uses a mixture of lanthanide oxides tungsten to improve their high-temperature properties.
  • Magnetic resonance imaging (MRI) uses the complex Gd (DOTA).
  • Currently,  lanthanides elements can also be used as anticancer agents as per research. The main role of the lanthanides in these studies is to inhibit proliferation of the cancer cells. Cerium and lanthanum have been especially studied for their role as anti-cancer agents.

The lanthanides have a low availability in the biosphere because of their sparse distribution in the earth’s crust and low aqueous solubility.

Solved Examples for You

Question: What are rare earth metals?

Answer: Lanthanides are ‘rare earth’ metals. However, the IUPAC disagrees with this term as the elements are neither rare nor earth.

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