The document discusses the lanthanides and actinides, which are groups of elements found below the main periodic table. There are a total of 30 elements between the lanthanides (elements 57-71) and actinides (elements 89-103). The lanthanides and actinides are often referred to as the "inner transition metals" and exhibit similar chemical properties to lanthanum and actinium, respectively.

2. The lanthanides and actinides are groups of elements in the periodic table.
They are the elements that are often listed below the main section of the
periodic table. There are thirty total elements in the lanthanides and actinides.
They are often called the "inner transition metals."
Lanthanides
The lanthanides are the elements with atomic numbers from 57 to 71. These
15 metals (along with scandium and yttrium) are often called the rare earth
elements. They are all silvery-white metals which are often found in the same
ores. They are called the lanthanides because they exhibit similar chemical
properties to lanthanum, the first element in the group.
Actinides
Actinides are the 15 elements with atomic numbers from 89 to 103. They are
named after the first element in the series, actinium. The actinides group
includes mostly man-made elements with only a few exceptions such as
uranium and thorium. The actinides are most known for the
elements uranium and plutonium which are used in nuclear reactors and
nuclear bombs.

3. 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.

6. The common oxidation state shown by all the lanthanides is + 3. Some
elements display +2 and +4 oxidation states but these are always less stable
than the group valency +3. The unusual oxidation states touches +2 and +4
exhibited by the lanthanides can be explained on the basis of extra stability
associated with empty, half filled and fully filled 4f subshell.
• Eu and Yb exhibit +2 oxidation states:
This is because in +2 oxidation State Europium and Ytterbium acquire f7 and f14
electronic configuration.
Eu2+ [Xe] 4f7, Yb2+[Xe] 4f14
• Ce and Tb exhibit +4 oxidation states:
This is because in +4 oxidation State Cerium and terbium acquire f0 and f7
electronic configuration which are supposed to be stable configuration
Ce4+[Xe] 4f0 , Tb4+[Xe] 4f7

8. • It is found that the most stable oxidation states of the elements up to
Uranium is the involving all the valence electrons.
• Neptunium form +7 state using all the valence electrons but this is
oxidising and the most stable is +5.
• Plutonium also shows states up to +7 an Americium up to +6 but the
most stable state drops to Pu4+ and Am3+ and latter elements tend to be
stable in +3 oxidation state.
• Berkelium in +4 state is stronger oxidising but is more stable than
Curium and americium in +4 state due to f7configuration.
• Similarly nobelium is markedly stable in the +2 state due to it's f14
configuration.

9. • Each energy level of an atom is described by
not only by its electronic configuration but also
its term symbol.
• The word term refers to energy level, so a term
symbol represents electronic state of a
particular type of electron.
• The ground state term symbol = 2S+1 L J

10. Elements with even atomic number are more
abudant than odd atomic number- Harkin’s rule
Even atomic number-more stable isotope
Odd atomic number-About two stable isotopes
Ce is as abudant as Copper
Pm Doesn’t occure naturally
Mattauch’s rule-If two elements with consecutive
atomic no have isotope of same weight,then one
of them is unstable.
All other elements have natural occurrence.

11. Bastnasite & Monazite are the main source of
Lanthanides.
Monazite- mixed phosphate (LnPO4)
Bastnasite-LnCO3F- Source of lighter Lanthanides
Techniques for separation:-
Precipitation
Complex formation
Solvent extraction
Valency change
Ion exchange

12.  Moving from left to right across a period,covalent
&ionic radii decreases:-Lanthanide Contraction
 Average contraction is about 0.2A°
 Consequences of contraction
Decrease in size from La to Lu
Hardness,B.p,M.p of elements increases Ce to Lu
Lu3+more hydrated(small) &La3+least hydrated(large)
Complex formed by Lu3+ is strong (Smallest ion)
La(OH)3 ,Ce(OH)3 are strong base & Lu(OH)3 is least basic

13. Metals of III state are elctro positive
Sum of the three ionisation energies is minimum
for La3+ ,Gd3+ Lu3+
Standard reduction potential is very high
Basicity decreases as ionic radii decreases from La
to Lu & from Ac to Lr
Metals react with Hydrogen to form hydrides &
these hydrides are decomposed by water and
react with oxygen
CeH2 +2H2O CeO2 + 2H2

14. • Anhydrous Halides Mx3 from metal & halogen
Ln2O3 + 6NH4Cl 300°c 2LnCl3 +6NH3+3H2O
LnCl3 .6H2O heat LnOCl + 5H2O + 2HCl
Hydrides of actinum:-
Uranium reacts with hydrogen at room
temperature to give hydride
U + H2 UH3
2UH3 + 4H2O 2UO2 + 7H2
UH3 + HCl UCl3 + 3H2
Oxides :-
UO2 - Black & U3O8 -Green black & UO3 –Orange
yellow

15.  Uranium exhibits +3 - +6 oxidation state.
 Most of the compounds formed by taking UO2
 UF6 is colourless, volatile solid.
 UF6 is vigorous fluorinating agent.
 UF6 + BCl3 UCl6 (Unstable)
UF6 + H2O UOF4 + 2HF
 UF4 is inert, sparingly soluble and green.
Oxides :-
UO2 - Black & U3O8 -Green black & UO3 –Orange
yellow

16. UO2(NO3 )2 .2H2O 350°c UO3
co,350°c UO2
U+O2 U3O8
700°c
All the oxides are basic & dissolve in acid
Some reactions of Fluoride
UO2
HF UF4
F
2,
240°c UF5
HF [UF6]-
HBr,65°c UF6 &[UF8]-
UF6 & UCl6 are octahedral but all other halides are
Polymeric & have higher coordination number.
 UF6 obtained from colourless crystals and a
powerful Fluorinating agent.
AmO2
2+ is a strong oxidising agent like KMnO4

17. Since f electrons are
buried,ligands are placed
with minimal inter ligand
repulsion.Ln3+ being
large,hard lewis acid
adopted with high
coordination number.
CN of [Ln(H2O)n ]3+ =9 for
early lanthanides & 8 for
later. Yb3+ forms 7 CN
complex [Yb(acac)3)H2O]
&large La3+ forms 8CN
complex [La(acac)3(H2O)2]

19. Trivalent ions are strongly coloured.Colour
depends on unpaired electrons.
 Ce3+ & Tb3+ are colourless & pale yellow
respectively due to strong absorption of 4f 5d
transition
 f0 ,f7 ,f14 ions are colourless
Spin-orbit coupling is more important than crystal
field splitting- Russel saunder coupling
Absorption due to f-f transition are sharpe & 4f-
5d are broad in Lanthanides.Exception –Lu3+

21. • Luminescence of Lanthanide complex
Irradiation with UV light causes fluroscence in
Ln3+ complex. However, in some cases very
low temperature is required to observe this.
Origin of fluroscence- 4f-4f transition
[ No transition being possible for f0 , f7 (spin
forbidden) & f14 ]
e.g. Eu3+ (red emission) , Tb3+ (green emission)
are commercially useful.
• Lanthanoid metals
Lanthanum and lanthanoids crystallise in one or
both cubic or HCP lattice except
Eu(Europium). Eu crystallises in BCC .

22.  All the Lanthanides with exceptions of La3+,Lu3+,Yb3+ &
Ce4+ are paramagnetic because they contain unpaired
electrons in the 4f orbital.
µs+L =√4S(S+1)+L(L+1)
S=spin quantum number,L=orbital quantum number
 In Lanthanides & Actinides the spin and orbital
contribution couples and give a new number ‘J’
 µ=g√J(J+1) where g=1+2J(J+1)
(S+1)-L(L+1)+J(J+1)
 In Actinides J is twice than that of
Lanthanides,magnetic properties same as Lanthanides

23. 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. They can also be used for
structural-alloy-modifying components of reactors.
Life Science
It is also possible for some elements, such as Thulium, to be used as portable x-ray sources.
Other elements, such as Europium, can be used as radiation sources for treatment of cancer

24. The MRI image is generated by the
information obtained from the 1H NMR
spectroscopic signals of water. The signal
intensity depends upon the proton
relaxation times and the concentration of
water.
The relaxation times can be altered and
the image enhanced , by using MRI
contrast agents. Coordination complexes
containing paramagnetic Gd3+ , Fe 3+ or
Mn2+ are potentially suitable as contrast
agents & of these, complexes containing
the Gd3+ ion have so far proved to be
especially useful. As a free ion , Gd3+ is
extremely toxic and therefore to minimise
side effects in patients , Gd3+ must be
introduced in the form of a complex that
will not dissociate in the body.

25. e.g. 1. [Gd(DTPA)(OH2)]2- - Magnevist – was
approved in 1988 for medical use as an
MRI contrast agent .
2. [Gd(DTPA-BMA)(OH2)] - Omniscan
3. [Gd(HP-DO3A)(OH2)] - Prohance
These three are classed as extra-cellular
contrast agents(Once injected,they are
distributed non-specifically throughout
extra cellular fluids). Elimination is easy
through kidney with a halflife of around 90
minutes.

26. • The magnetic field experienced by a proton is very different from
that of the applied field when a paramagnetic metal centre is
present. This results in the Ᵹ range over which the 1H NMR
spectroscopic signals appear being larger than in a spectrum of
related diamagnetic complex .
Signals for protons close to the paramagnetic metal centre are
significantly shifted and this has the effect of “spreading out” the
spectrum.
• Generally, low- and midfield NMR instruments are used daily for
research, and in these case Paramagnetic NMR shift reagents may
be used to disperse overlapping signals.
• Ln complexes are routinely employed as NMR shift reagents. The
addition of small amount of a shift reagent to a solution of an
organic compound can lead to an equilibrium being established
between the free and coordinated organic species. The result is
that signals due to the organic species which originally overlapped,
spread out , and the spectrum becomes easier to interpret.

27. e.g. Europium(III) complex
shown below is a
commercially available shift
reagent.(Resolve-AITM) ---
used to resolve
diastereomeric mixtures.

29. One of the driving forces behind the study of organolanthanoid
complexes is the ability of some of them to act as highly
effective catalysts in organic transformations including
hydrogenation,
hydrosilylation, hydroboration and hydroamination reactions
and the cyclization and polymerization of alkenes. The
availability of a range of different lanthanoid metals coupled
with a variety of ligands provides a means of systematically
altering the properties of a series of organometallic complexes.
In turn, this leads to controlled variation in their catalytic behaviour,
including selectivity.
The presence of an (Z5-C5R5)Ln or (Z5-C5R5)2Ln unit in an
organolanthanoid complex is a typical feature, and often
R¼Me. When R¼H, complexes tend to be poorly soluble in
hydrocarbon solvents and catalytic activity is typically low.
Hydrocarbon solvents are generally used for catalytic reactions
because coordinating solvents (e.g. ethers) bind to the Ln3þ
centre, hindering association of the metal with the desired
organic substrate. In designing a potential catalyst, attention
must be paid to the accessibility of the metal centre to the
substrate. Dimerization of organolanthanoid complexes via
bridge formation is a characteristic feature. This is a disadvantage
in a catalyst because the metal centre is less accessible to a
substrate than in a monomer. An inherent problem of the (Z5-
C5R5)2Ln-containing systems is that the steric demands of
substituted cyclopentadienyl ligands may hinder the catalytic
activity of the metal centre. One strategy to retain an accessible
Ln centre is to increase the tilt angle between two Z5-C5R5
units by attaching them together as illustrated

31. QUESTIONS
2003, GATE
25. The ligand field bands of lanthanide complexes are generally
sharper than those of transition metal complexes because
(a) Transitions are allowed for lanthanide complexes
(b) intensity of the bands are higher for lanthanide complexes
(c) f-orbital have higher energy than d-orbital
(d) f-orbital, compared to d-orbital interacts less effectively with
ligand

32. 2005, GATE
63. LFSEs are smaller for lanthanides compared to TMs in the
oxidation state because
(a) Size of lanthanide ion are larger
(b) f orbitals interact less effectively with ligands
(c) size of lanthanide ion are smaller
(d) lanthanides favour oxygen donor ligands
64. The lanthanide complex (where, acac = acetylacetonate; phen-
1, 10-phenanthroline ) that do not have square antiprismatic
structure is
(a) [Ce(NO3)6 ]2- (b) [La(acac)3(H2O)2]
(c) [Ce(acac)4] (d) [Eu(acac)3(phen)]

33. 2007, GATE
16. The difference in the measured and calculated magnetic
moment (based on spin-orbit coupling) is observed for
(a) Pm3+ (b) Eu3+ (c) Dy3+ (d) Lu3+
50. The separation of trivalent lanthanide ions, Lu3+ ,Yb3+ , Dy3+ ,
Eu3+ can be effectively done by cation exchange resin using
ammonium o-hydroxy iso-butyrate as the eluent. The order in
which the ions will be separated is
(a) Lu3+ ,Yb3+ , Dy3+ , Eu3+
(b) Eu3+, Dy3+, Yb3+, Lu3+
(c) Dy3+, Yb3+, Eu3+, Lu3+
(d) Yb3+, Dy3+, Lu3+, Eu3+

34. 2013, GATE
43. The correct electronic configuration and spin only magnetic
moment of Gd3+ (at. no. 64) are
(a) [Xe] 4f7 and 7.9 BM
(b) [Xe] 4f7 and 8.9 BM
(c) [Xe] 4f6 5d1 and 7.9 BM
(d) [Rn] 5f7 and 7.9 BM

35. 2017, GATE
11. The lanthanide ion that exhibits colour in aqueous solution is
(a) La(III) (b) Eu(III)
(c) Gd(III) (d) Lu(III)
2018, GATE
37. Generally, the coordination number and the nature of the
electronic absorption band (f f transition) of lanthanide
(III) ion in their complexes are, respectively,
(a) Greater than 6 and sharp
(b) 6 and broad
(c) less than 6 and sharp
(d) greater than 6 and broad