Lanthanide Chemistry

A brief introduction to lanthanide elements is given.
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Along with their physical and chemical properties are also shown. Helpful for quick understanding on lanthanide series.

1. Lanthanide Chemistry

2. Introduction The term "lanthanide" was introduced by Victor Goldschmidt in 1925 Lanthanide series comprises the fifteen metallic chemical elements with atomic numbers 57 through 71, from lanthanum through lutetium The elements in which the additional electrons enter into (n-2)f Orbitals are called the inner transition elements. The valence shell electronic configuration of the lanthanides is ( n-2)f1_14 (n-1)d0-10 ns2

3. POSITION IN PERIODIC TABLE Their position are as follow. If we put  lanthanides and actinides  in to the  Periodic Table  like transition metals, the  table  will be way too wide. The two rows of elements present at the bottom of the  periodic table  are called the 4f series or lanthanoids and 5f or actanoids . They are also called inner transition elements.

4. NATURE OF LANTHANIDES Lanthanide metals are generally soft malleable and ductile in nature.

5. In case of Ba 56 ,6s orbital is completely filled and in case of La 57 5d orbital is singly filled…. But after crossing La57 , The nuclear charge increases by one unit and 4f orbital which is Much in energy fall than fd is filled first. An exception is shown by GADOLINIUM.Its outermost electronic Configuration s [ Xe ]4f7 5d1 6s2.though there is a huge energy gap Between 4f and 5d,Gd tends to remsin in 4f7 confg in order to Attain a half filled stability.

6. An important characteristic shown by lanthanides is LANTHANIDE CONTRACTION REASON FOR LANTHANIDE CONTRACTION The shielding effect of 4f is very smaller than d orbital as 4f Orbital is much diffuse in nature. AS A RESULT IONIC RADII DECREASE

7. CONSEQUENCES OF LANTHANIDE CONTRACTION Post lanthanide elements such as Zr and Hf shows similar I onic radii though they belong to first and second transition series 2.L anthanides show similar physical and chemical properties.so they are hard to seperate

8. Oxidation State Preferences Ionization For any given Lanthanide : ™ As successive electrons are removed from neutral Ln the stabilizing effect on the orbitals is related to their principal quantum number, 4f > 5d > 6s. ™ For Ln2+ (except for La & Gd ) the configuration is [ Xe ]4fn ™ For Ln3+ the configuration is always [ Xe ]4fn ™ The 4f binding energy is so great that remaining 4f electrons are regarded as "core-like" (i.e. incapable of modification by chemical means), except Ce . Therefore in almost all cases Ln3+ provides the best energetics : Atomization ∆ atmH follows the inverse trend to I3, and therefore also to (I1 + I2 + I3). Metallic bonding is correlated with ease of ionization to Ln3+ state. This trend is modified slightly due to the different structures of the Ln metals

9. Oxidation State Preferences ( CONTENUED )

10. Oxidation State Preferences (CONTENUED)

11. COLOUR OF LANTHANIDES The colour of the lanthanides emerge from f to f transitions . f → f transitions are much weaker and narrower than those from d → d transitions This makes the colours of lanthanide complexes far fainter than those of transition metal complexes.

12. MAGNETIC PROPERTIES OF LANTHANIDES Lanthanide ions may be diamagnetic or Paramagnetic Ferromagnetism / Anti-Ferromagnetism / Ferrimagnetism Lanthanide metals and alloys have interesting ordered magnetism effects SmCo5, Nd2Fe14B permanent magnets – FERROMAGNETIC Rare Earth Garnets e.g. Ln3Fe5O12 and Y3Fe5O12. FERRIMAGNETISM shows an unusual temperature-dependence

13. SEPERATION OF LANTHANIDES The similarity in ionic radius between adjacent lanthanide elements makes it difficult to separate them from each other in naturally occurring ores and other mixtures. thatS why the are termed “RARE EARTH ELEMENT” 2/3 of world production is actually used mixed in the proportions occurring naturally in the ore 1. Cerium & Europium may be extracted Chemically 2. Separation by Fractionation: Small Scale methods used originally Current Small Scale Lab Separation: • Ion-Exchange Displacement Column 3.Current Large Scale Industrial Separation: Solvent Extraction

14. APPLICATION OF LANTHANIDES Metals and Alloys The pure metals of the Lanthanides have little use. However, the alloys of the metals can be very useful. For example, the alloys of Cerium have been used for metallurgical applications due to their strong reducing abilities. Non-nuclear The Lanthanides can also be used for ceramic purposes. The almost glass-like covering of a ceramic dish can be created with the lanthanides. Nuclear Like the Actinides, the Lanthanides can be used for nuclear purposes. The hydrides can be used as hydrogen-moderator carriers. The oxides can be used as diluents in nuclear fields. The metals are good for being used as structural components. The can also be used for structural-alloy-modifying components of reactors. Life Science It is also possible for some elements, such as Tm, to be used as portable x-ray sources. Other elements, such as Eu , can be used as radiation sources for treatment of cancer.

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