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Lanthanides are also known as rare earth elements. They are from the family of inner transition elements. They are present at the bottom of the periodic table.

The first lanthanide element was discovered in 1787. It was first found in mineral form, and later it was separated into its constituent lanthanide elements. Although it is known as rare earth metal, it is found in abundant amounts.

Currently, we know more than 100 minerals that contain a low or high amount of rare earth elements.

Lanthanides consist of 14 elements, including atomic number 57 (Lanthanum) to 71 (Lutetium).

Uses of lanthanides

Lanthanide complexes help in the detection of cancer. Because of their luminescence and magnetic properties they are used in the medical field for diagnostics and therapies. Many lanthanide compounds act as catalysts too. Some of them are also used to make nuclear weapons and rocket fuels. Some oxides of lanthanides are also used in fluorescent lamps because of their light-emitting nature.

Properties of lanthanides

Lanthanides are a group of rare earth metals consisting of homogeneous elements of 14 pieces ranging from atomic no 57 to 71. The electronic configuration of lanthanides is

(n-2)f¹⁻¹⁴,(n-1)d¹⁻¹0,ns²

Mostly lanthanide elements are silver-coloured. They are soft, and you can even cut lanthanide with a knife. They are easily found in nature but it is too difficult to separate them. The first element of this series is lanthanum, and the last one is lutetium. The chemical properties of lanthanides are similar to each other because of a more negligible difference in their sizes. Lanthanides have higher densities than other elements in the periodic table.

Physical and chemical properties of lanthanides

The physical and chemical properties of lanthanides may be discussed as follows:

  1. Lustrous: Lanthanides are lustrous, i.e. they  produce a shiny effect and have a silvery appearance.
  1. Soft metal: Lanthanides are too soft and can be cut with a knife. Compounds formed by lanthanides are mostly trivalent, but they can also include other divalent or trivalent compounds.
  1. Lanthanide contraction: Due to lanthanide contraction, there is an increase in the nuclear charge between the outermost shell and the nucleus. As a result, the  atomic and ionic radii decrease. When we go from left to right in the periodic table, there is a decrease in the size of lanthanides with a higher atomic number. There is also a decrease in the covalent nature, which reduces the fundamental strength of hydroxides of lanthanides. Due to lanthanide contraction, decrease in atomic size and the formation of many coordination compounds because of their smaller size and higher nuclear charge are observed. 
  1. Not easy to separate: It is not easy to separate constituent lanthanide elements because their chemical properties are very similar. Difficulty in separating lanthanide elements leads to a reduction in the fundamental strength of hydroxides of lanthanides resulting in the formation of coordination compounds.
  1. Smaller atomic and ionic radii: Lanthanides have smaller atomic and ionic radii due to lanthanide contraction.
  1. Higher melting and boiling point: Lanthanide has higher melting and boiling point than other elements in the periodic table, but there is no regularity in the trend.
  1. Electronegativity: Electronegativity is the ease with which electrons can be taken. Electronegativity increases when we go up in the lanthanide series.
  1. Ionisation: Ionisation energy is the energy needed to remove electrons from the outermost shell of a neutral atom. Because of lanthanide contraction, it has higher ionisation energy as there is too much attraction between the nucleus and the outer electrons. It will need more energy to remove electrons from the outermost shell.
  1. Coloured ions: Lanthanide ions are coloured. When any element absorbs the frequency of light, it will show colours complementary to the light absorbed. The inner transition element absorbs the frequency of lights present in the visible region and produces colourful ions.
  2. Oxidation states: Lanthanides show various oxidation states like +2,+3, +4 and others. Their most common oxidation state is +3. By gaining and losing electrons, they become good oxidising and reducing agents.

Conclusion

Lanthanides are the elements off the block; they are also known as inner transition elements. Their valence shell electron enters into pre penultimate shell (n-2)f orbitals, which are inner to the penultimate shell. Lanthanides exhibit many physical and chemical characteristics and are used in various fields.