Important Topic: Lanthanides

Introduction

Lanthanides are the world’s rarest table of time dates. It means that elements with atomic numbers from 58 to 71 follow the element Lanthanum. They are known as rare earth metals as the occurrence of these elements is very low (3 × 10-⁴% of the Earth’s crust). They are found in ‘monazite’ sands like lanthanide orthophosphates.

The term ‘lanthanide’ was first coined in 1925 by Norwegian mineral expert Victor Goldschmidt. The lanthanide family contains fifteen iron elements (ranging from lanthanum to lutetium), all except one of which are f-block elements. The valence electrons of these elements are also found in the 4f orbital. However, lanthanum is a d-block component with the electronic configuration of Xe5d¹6s².

Lanthanides elements are very dense, with a density ranging from 6.1 to 9.8 grams per cubic centimetre. Like most metals, these elements have a high melting point (approximately 800 to 1600 degrees Celsius) and high boiling points (approximately 1200 to 3500 ° C). All lanthanides are best known for making Ln³⁺ cations.

Lanthanides are also more dense metals and even soluble points higher than d-block materials. They produce alloys and other metals. These are the features of the f block, also called internal conversion tools. Internal ions/elements can have electrons in s, d, and f- orbitals.

Lanthanides Contraction

The ionic radius or ionic ion of the trip positive lanthanide decreases gradually from La to Lu due to an increase in nuclear charge and electrons entering the internal orbital (n-2) f. This gradual decrease in the number of growing atoms is known as lanthanides contraction.

Effects of Lanthanides Contraction

The points listed below will show the effect of lanthanide depletion.

• Atomic Size – The third-order transformation series is almost identical to the atomic sequence of the second transformation. For example, radius N_b = Ta radius and Z_r radius = H_f radius, etc.
• Difficulty in Separating Lanthanides – Since there is only a small change in the ionic radii of Lanthanides and their chemical properties are the same, this makes the separation of the lanthanides element difficult in a pure state.
• Impact on the Basic Power of Hydroxides – As the size of lanthanides decreases from La to Lu and the combined characteristic of hydroxides increases, hence its basic strength decreases. Therefore, Lu (OH)₃ is less basic and La (OH)₃ is more basic.
• Complex Design – Due to the small size and high nuclear cost, they often make links. Complexity rises from La₃ + to Lu₃⁺.

Lanthanide Series Buildings

As an instrument of change In the periodic table, if we consider the series of lanthanides and actinides, the table will be much wider. These two series is called the 4f or Lanthanide series and the 5f or Actinides series present under the periodic table. Combined, the 4f and 5f series is called internal transformation elements.

All the elements in the series are very similar to lanthanum and each with its own physical and chemical properties. Some important features of lanthanides are listed below.

• They are silver-coloured and shiny.
• They are soft metal and can be cut with a knife.
• The elements of lanthanide have a different tendency to react to basic dependence. Some take longer to respond while others respond more strongly.
• Lanthanides can be brittle or igneous if it is contaminated with other metals or non-metals.
• Magnetic.
• In particular, they form a trivalent compound and can sometimes form divalent or tetravalent compounds as well.

Lanthanides Physical Properties

The visual features of Lanthanides are given in the following.

• Melting Points – These have a relatively high melting point, but there is no definite practice in the area of ​​boiling and melting lanthanides.
• Density – As a measure of the weight of an object in its volume, the density of the d-block elements will be higher than the s-block elements. The density trend will be the reversal of the atomic radii. During a series of internal changes, overcrowding increases with the number of atoms growing over time.
• They have a maximum density between 6.77 to 9.74 g cm^-3. It increases with the number of atoms growing.
• Magnetic Properties – Materials are classified based on their interaction with a magnetic field such as Diamagnetic (if fired), Paramagnetic (if attracted).
• Lanthanide ions/atoms other than f₀ and f₁₄ are naturally paramagnetic due to the unpaired electrons in orbitals. Therefore, Yb₂⁺, Ce₄⁺, and Lu₃⁺ are diamagnetic.
• Unconnected electrons contribute to ‘magnetic minute rotation’ and ‘magnetic rotation moment.’ Both electron times are taken into account when calculating the total magnetic moment.

Electronic Configuration for Lanthanides

The first f-block Lanthanides contains the electronic configuration of Xe 4f₁-14 5_d 0 – 16s² for 14 lanthanides. Promethium (Pm) with a number of atoms 61, is the only synthetic radioactive element. The energy of the 5d and 4f electrons is almost identical, so the 5d orbital remains empty and the electrons enter the 4f orbital.

The exception to the gadolinium case is Gd (Z = 64), in which the electron enters the 5d orbital due to the presence of lutetium (Z = 71) and the partially full orbital enter the 5d orbital.

A series of lanthanide or lanthanoid chemical compounds comprise 15 metal elements with atomic numbers 57–71, from lanthanum to lutetium. These elements, along with the same chemical elements scandium and yttrium, are commonly known collectively as rare earth elements or rare earth metals.

FAQ’s

Q. Explain the Use of Lanthanides?

Ans: A few uses of Lanthanide are listed below.

Ceramic Applications – Oxides of type Ce (III), Ce (IV) are used in glass polishing powders, while Nd and Pr oxides are widely used in glass counting and in the production of standard light filters.

Metallurgical Applications – Some lanthanide element alloys find critical metallurgical applications as reducing agents. For example, Misch metals (Ce- 30 to 35%).

Electrical Appliances – Ferromagnetic garnets of type 3Ln2O3.5Fe2O3 can be used on microwave devices.

Catalytic Applications – Other lanthanide compounds can be used as catalysts. For example, Cerium phosphate is used as a catalyst for the breakdown of petroleum.

Nuclear Systems – Some of their compounds, including these compounds, are used in defence systems, nuclear control systems, and flexible applications. Eu – 153, Sm – 140, Gd- 157, Gd- 155, and Dy-164 are other important isotopes used in nuclear technology.

Ceramic sulphate is also an excellent oxidizing analytical agent.

Lanthanide oxides are just as effective as phosphorus in bright colours.

Q. Describe the Oxidation Status of Lanthanides?

Ans: All the elements in the lanthanide series show a +3 state of oxidation. It is believed that other metals such as europium, samarium, and ytterbium also show +2 oxidation states in the past. Further research on these metals and their compounds have shown that all lanthanide series compounds show an oxidation status of +2 in their solvent compounds.

Some lanthanide series metals occasionally show +4 oxidation states. This type of uneven distribution of oxidation conditions between metals is specified in the high stability of half-filled, empty, or fully filled subshells.

The stability of the f-subshell affects the state of lanthanides’ oxidation so that the oxidation +4 level of cerium is favourable because it receives a decent gas configuration. However, it returns to the state of oxidation +3 and acts as a strong oxidant and is able to release water even though it will move slowly.

Oxidation +4 status is also indicated by the oxides of Praseodymium (Pr), Dysprosium (Dy), Neodymium (Nd), and Terbium (Tb).