Profile
Settings
Refer your friends
Sign out
Scientists discovered lanthanides in 1787 in Ytterby, Sweden, in a strange black mineral known as Gadolinite. Later, the scientists separated the Lanthanide elements from this mineral. Professor Gadolin obtained yttria from the mineral in 1794, which is an impure form of yttrium oxide. Berzelius and Klaproth secluded the first Cerium compound in 1803. Moseley later used X-ray spectra to prove 14 elements between Lanthanum and Hafnium. The scientists later separated the other elements from the same mineral. These elements were first referred to as ‘rare earth’ elements because they are obtained from relatively rare minerals. However, it can be misleading due to the abundance of Lanthanide elements. The name Lanthanides came from the first element in the series, Lanthanum.
Properties of lanthanides
A knife can cut lanthanides because they are soft. Praseodymium, neodymium, lanthanum, cerium, and europium are highly reactive. Their exposure to oxygen leads to the formation of an oxide. To prevent their tarnishing, lanthanides are kept in mineral oil.
For example, lutetium and gadolinium do not oxidize until we expose them to air for a long time. However, lanthanides are a “temperamental” class. They corrode easily when we contaminate them with other metals, such as calcium, and become brittle when we contaminate them with nonmetals, such as oxygen or nitrogen. Boiling points vary from 819°C for ytterbium to 1,663°C for lutetium, depending on the level of contamination.
Lanthanides produce hydrogen gas when reacting to either hot or cold water. They readily burn in the air. Lanthanides lose three of their outer electrons when they react with another element to form an electric charge of +3 atoms. Lanthanides create less stable +2 or +4 ions. Lanthanides form ionic compounds with other substances, such as fluorine.
Is the occurrence of lanthanides Really “Rare”?
Because of the difficulty in extracting lanthanides from compounds with other substances, which also include other lanthanides, they were once known as rare earth metals. As we’ll see, this isn’t the case anymore. Thulium, the rarest lanthanides, is present more than mercury or arsenic, and no one considers them rare substances. The Earth’s crust contains 0.2 ppm thulium. The most abundant lanthanide, cerium, has 46 ppm.
The lanthanides are rare if we call rarity in obtaining an element in pure form. Because they share many properties and tend to congregate in the same substances, the lanthanides took more than a century to be identified and isolated. The progress has a common pattern – after a chemist discovered a new lanthanide, another scientist discovered another lanthanide in the same sample that the first chemist thought was a single element. Hene the lanthanides evolved like Russian nesting dolls.
Extraction of lanthanides
Though scientists discovered most lanthanides in Scandinavia, they are now present in India, Australia, South Africa, Brazil, and the USA. Scientists mined most lanthanide mass available to industry and science from monazite, a kind of heavy and dark sand. Monazite is the primary source of lanthanide.
We use a substance with low solubility to separate lanthanides from other elements. For this, fluorides and oxalates, which have low solubility, are ideal. We use ion exchange to separate lanthanide elements after they separate from non-lanthanide elements.
Lanthanide atoms radii decrease with increasing atomic number. The contraction of the lanthanide atoms helps in the ion exchange, and it is the lanthanide contraction. We mix lanthanides in the ionic solution and pass them through a long resin column. Depending on their size, many lanthanide ions bond with resin less or more tightly.
Then, lanthanides washed out of the ion exchange column and into different solutions. We separate them one by one and then mix them with acid and heat them to form an oxide. The oxide is then converted to fluoride or chloride and reduced to metallic form using calcium.
Electron Configuration
The electron configurations of Lanthanides are similar, which explains most of their physical similarities. These elements differ from the main group elements because they have electrons in the f orbital – energy in the 4f subshell drops below the 5d subshell after lanthanum. The electron fills the 4f subshell before the 5d subshell.
These elements’ electron configurations are established primarily through experiments. The method relies on the fact that each line in an emission spectrum reveals the energy change involved in an electron’s energy level transition. The problem with this technique for Lanthanide elements is that the 4f and 5d subshells have similar energy levels, making it difficult to tell the difference between them.
The Lanthanide Contraction, in which the 5s and 5p orbitals penetrate the 4f subshell, is another important feature of Lanthanides. It means the 4f orbital is not shielded from the increasing nuclear change, causing the atomic radius to decrease throughout the series.
Conclusion
Lanthanides are at the bottom of the periodic table, separated from the main body of the chart by two rows. Lanthanides, including lanthanum and the 14 other elements in the lanthanide series, were formerly known as “rare earth” metals. They aren’t that rare; many of them are just as, or more, common as elements like mercury. In addition to their silvery colour and high reactivity, they are difficult to extract and are particularly susceptible to contamination because their difficult extraction is a key characteristic. These components are present in everything from cigarette lighters to TV screens and coloured glass to nuclear reactor control rods.
