Lanthanides were originally known as “rare earth” metals because they were made up of lanthanum and the 14 elements of the lanthanide series. In fact, several of them are as common as elements like mercury. They are, however, difficult to remove, a quality that identifies them as much as their silvery hue, reactivity, and contamination sensitivity.
The 14 elements that precede lanthanum on the periodic table, with atomic numbers 58 through 71, make up the lanthanide series. Due to similarities in features that characterise each group, these 14 and the actinides (atomic numbers 90 through 103) are excluded from the periodic table.
Properties of lanthanides
Although they are metals, several lanthanides are bright and silvery in look and maybe sliced with a knife. When exposed to oxygen, they produce an oxide coating. An oxide is a chemical made up of a metal and oxygen. These five lanthanides are stored in mineral oil to prevent them from tarnishing.
Gadolinium and lutetium, for example, do not oxidise until they have been exposed to air for an extended period. Lanthanides, on the other hand, have a reputation for being “temperamental”. They corrode readily if they come into contact with other metals, such as calcium, and they become brittle if they come into contact with nonmetals, such as nitrogen or oxygen.
Lanthanides create hydrogen gas when they react quickly with hot water or more gradually with cold water. They are also capable of reacting with oxygen, and they easily burn in air, as previously stated. When a lanthanide combines with another element to produce a compound, it often loses three of its outer electrons, forming tripositive ions or atoms with a positive electric charge.
For lanthanides, +3 is the most stable ion; nevertheless, less stable +2 or +4 ions can form. Lanthanides and other chemicals, particularly fluorine, tend to create ionic compounds or compounds having either positive or negative ions.
Physical properties of lanthanides
- Because density is defined as the ratio of a substance’s mass to its volume, d-block elements will have a higher density than s-block elements.
- The density trend in the inner transition series will be the inverse of atomic radii. That is, density will rise as the atomic number grows over time. Their density is high, ranging from 6.77 to 9.74 g cm-3. It grows in proportion to the atomic number.
- Lanthanides have a high melting point, yet their boiling and melting temperatures have no recognisable pattern.
- Materials are classified as diamagnetic or paramagnetic depending on whether or not they are repelled by a magnetic field. Lanthanide atoms and ions other than f0 and f14 are paramagnetic by nature due to unpaired electrons in orbitals.
Chemical properties of lanthanides
- Lanthanides make colourful solutions that fade to a light yellow tone.
- They show a variety of oxidation states, with +3 being the most prevalent.
- Except for gadolinium and lutetium that slowly discolour in air, very reactive metals can quickly produce oxide coatings when exposed to air.
- When it comes to binding, more electronegative components are preferred.
- When heated, it dissolves quickly in acid, ignites in air, and interacts with halogens, sulphur, hydrogen, carbon, and nitrogen.
Magnetic properties of lanthanides
- Because they do not contain unpaired electrons, certain lanthanide ions are diamagnetic, whereas the rest of the elements are paramagnetic at normal temperatures.
- Below the Curie temperature, which is often quite low, they are ferromagnetic.
- The ‘spin magnetic moment’ and ‘orbital magnetic moment’, respectively, are influenced by unpaired electrons. When computing the total magnetic moment, both electron moments are considered.
Mechanical properties of lanthanides
- Rare-earth metals aren’t particularly weak or strong metals, although they have considerable ductility.
- It is difficult to compare published results in the literature because mechanical characteristics are so highly influenced by the purity of the metals as well as their thermal history.
- As would be predicted for a divalent metal, ytterbium’s strength (europium’s strength has not been tested) is significantly lower, at 58 MPa, and its ductility is higher, at roughly 45 per cent.
Consequences of lanthanide contraction
- Atomic size
- Difficulty in the separation of lanthanides
- Effect on the basic strength of hydroxides
- Complex formation
- Electronegativity
Uses and applications of lanthanides
- To provide materials strength and toughness.
- Because of its excellent reducing ability, it is used in metallurgical applications.
- As a catalyst for the production of glasses
- An antique television sets’ cathode ray tubes.
- Possibility of medicinal use as an anticancer agent.
Characteristics
- Lanthanide metals are soft, but as the series progresses, their hardness rises.
- Lanthanide metals have moderately high resistivity, ranging between 29 and 134 Ohm cm.
- Lanthanides have a lot of paramagnetic properties. At temperatures below 16 °C, gadolinium turns ferromagnetic (Curie point).
- Non-radioactive lanthanides are regarded as having minimal toxicity in comparison to most other non-dietary elements.
- Odd-numbered elements are less plentiful than their even-numbered neighbours, according to the Oddo-Harkins rule.
Conclusion
Despite the fact that some lanthanides have restricted applications, they may be found in everything from cigarette lighters to television screens, as well as tinted glass and nuclear reactor control rods.