Inner Transition Element, electronic configuration lanthanide and actinide, lanthanide contraction & consequences, oxidation state, magnetic properties, ion-exchange method for separation, similarities, and differences of lanthanide and actinide

4. Introduction to the Rare Earth Elements
4

5. Content :
1. f-Block elements
2. Introduction to lanthanides
3. Oxidation state
4. lanthanide contraction
5. Chemical reactivity
6. Introduction of Actinides
7. Comparison of actinides with lanthanides

6. Inner transition Element
The elements in which the additional electrons enters
(n-2)f orbital are called inner transition elements. The valence shell
electronic configuration of these elements can be represented as
(n – 2)f0-14(n – 1)d0-1ns2.
4f inner transition metals are known as lanthanides because
they come immediately after lanthanum
5f inner transition metals are known as actinide because they
come immediately after actinium.

7. Electronic Configuration
Element Symbol Z Ln Ln3+ Radius
Ln3+/ pm
Lanthanum La 57 [Xe]6s25d1 [Xe]4f0 116
Cerium Ce 58 [Xe]4f16s25d1 [Xe]4f1 114
Praseodymium Pr 59 [Xe]4f36s2 [Xe]4f2 113
Neodymium Nd 60 [Xe]4f46s2 [Xe]4f3 111
Promethium Pm 61 [Xe]4f56s2 [Xe]4f4 109
Samarium Sm 62 [Xe]4f66s2 [Xe]4f5 108
Europium Eu 63 [Xe]4f76s2 [Xe]4f6 107
Gadolinium Gd 64 [Xe]4f76s25d1 [Xe]4f7 105
Terbium Tb 65 [Xe] 4f96s2 [Xe]4f8 104
Dysprosium Dy 66 [Xe] 4f106s2 [Xe]4f9 103
Holmium Ho 67 [Xe] 4f116s2 [Xe]4f10 102
Erbium Er 68 [Xe] 4f126s2 [Xe]4f11 100
Thulium Tm 69 [Xe] 4f136s2 [Xe]4f12 99
Ytterbium Yb 70 [Xe] 4f146s2 [Xe]4f13 99
Lutetium Lu 71 [Xe] 4f146s25d1 [Xe]4f14 98

8. Atomic and ionic sizes:
The Lanthanide Contraction
As the atomic number increases, each succeeding element contains one
more electron in the 4f orbital and one proton in the nucleus. The 4f electrons
are ineffective in screening the outer electrons from the nucleus causing
imperfect shielding. As a result, there is a gradual increase in the nucleus
attraction for the outer electrons. Consequently gradual decrease in size
occur. This is called lanthanide contraction

11. Explain the cause and two consequences of lanthanide
contraction.
The poor shielding effect of f-electrons is cause of lanthanide
contraction.
 The nuclear charge increases by +1 unit
Consequences :
1.Electropositive or metallic nature-
lanthanum is most metallic while Lu is least metallic
2. Basic character of oxide and hydroxide(Ln(OH)3 & Ln2O3)
La(OH)3> Ce(OH)3 > Pr(OH)3 Yb(OH)3 > Lu(OH)3
Most Basic least basic
3. Ionic Character
La Most ionic Lu least ionic(covalent)
4.Electronegativity
slight increase La ……….Lu
5. Decomposition temp. of oxy salt
La(NO3)3 higher temp Lu(NO3)3 lower temp
6.Complex formation
lanthanide the tendency to form complexes from La to Lu
7. Difficulty in separation of lanthanides

12. Why Zr and Hf have almost similar atomic radii?
Zr and Hf have almost similar atomic radii as a consequence of
lanthanide contraction due to which their properties becomes similar.

13. Magnetic properties
Lanthanides have very high magnetic susceptibilities due to
their large numbers of unpaired f-electrons.
The lanthanide ions other then the f 0 type (La3+ and Ce3+)
and the f14 type (Yb2+ and Lu3+) are all paramagnetic. The
paramagnetic rises to the maximum in neodymium.
The strongest known magnets contain lanthanides (eg. Nd-Fe-B, Sm-Fe-N,
and Sm-Co).
Lanthanide complexes are used in MRI
(medical resonance imaging), eg.
[Gd(III)(dtpa)]2-

14. Oxidation States
Predominantly +3 oxidation state.
Occasionally +2 and +4 ions in solution or in solid compounds are also
obtained.
Ce+4 (f0), Tb+4(f7),
Eu2+(f7), Yb2+(f14)
This irregularity
arises mainly from
the extra stability
of empty, half
filled or filled f
subshell.

15. Why Sm2+, Eu2+, and Yb2+ ions in solutions are good reducing
agents but an aqueous solution of Ce4+ is a good oxidizing agent?
The most stable oxidation state of lanthanides is +3. Hence the ions in
+2 oxidation state tend to change +3 state by loss of electron acting
as reducing agents whereas those in +4 oxidation state tend to
change to +3 oxidation state by gain of electron acting as a good
oxidizing agent in aqueous solution.

16. Irradiation of some Lanthanide(III) complexes with UV light causes
them to fluoresce
The origin of fluorescence is 4f-4f transitions.
–the excited state produced decays to the ground state with
emission of energy.
Some examples are Eu3+ (red) and Tb3+ (green)
They can be used as phosphors in television sets and fluorescent
lighting.
These applications are specific to lanthanide ions because of the
sharp transitions observed.

17. Ion exchange method
Ln3+ + 3H+ Ln(resin)3 +3H+(aq)
Ln(resin)3 +3H+(aq) +(citrate)3- Ln(citrate) + 3H resin
Eluting agent

18. Uses
Best single use of the lanthanides is for the production of alloy steels for
plates and pipes.
A well known alloy is misch metal which consists of a lanthanide metal (~95%)
and iron (~5%) and traces of S, C, Ca and Al. A good deal of misch metal is
used in Mg based alloy to produce bullets, shell and lighter flint.
Mixed oxides of lanthanides are employed as catalysts
in petroleum cracking.

19. The Actinides
Result from the filling of the 5f orbital.
The others must be made by nuclear processes.
Only Th and U occur naturally-both are more abundant in the
earth’s crust than tin.
All isotopes are radioactive, with only 232Th, 235U, 238U and
244Pu having long half-lives.

20. properties of actinides
The dominant oxidation state of actinides is +3. Actinides also
exhibit an oxidation state of +4. Some actinides such as uranium,
neptunium and plutonium also exhibit an oxidation state of +6.
The actinides show actinide contraction (like lanthanide contraction)
due to poor shielding of the nuclear charge by 5f electrons.
All the actinides are radioactive. Actinides are radioactive in
nature. So the study of their chemistry is difficult in the
laboratory. Their chemistry is studied using tracer techniques.

21. Electronic configuration
Element Symbol Z Ln Ln3+ Radius
Ln3+/ pm
Actinium Ac 89 [Rn] 6d17s2 [Rn]4f0 111
Thorium Th 90 [Rn ]5d27s2 [Rn]4f1
Protactinium Pa 91 [Rn]5f26d17s2 [Rn]4f2
Uranium U 92 [Rn]5f36d17s2 [Rn]4f3 103
Neptunium Np 93 [Rn]5f46d17s2 [Rn]4f4 101
Plutonium Pu 94 [Rn]5f67s2 [Rn]4f5 100
Americium Am 95 [Rn]5f77s2 [Rn]4f6 99
Curium Cm 96 [Rn]5f76d17s2 [Rn]4f7 99
Berkelium Bk 97 [Rn]5f97s2 [Rn]4f8 98
Californium Cf 98 [Rn]5f107s2 [Rn]4f9 98
Einsteinium Es 99 [Rn]5f117s2 [Rn]4f10
Fermium Fm 100 [Rn]5f127s2 [Rn]4f11
Mendelevium Md 101 [Rn]5f137s2 [Rn]4f12
Nobelium No 102 [Rn]5f147s2 [Rn]4f13
Lawrencium Lr 103 [Rn]5f146d17s2 [Rn]4f14

22. Element Symbol At.
No.
Electronic
Conf.
Oxidation State
Actinium Ac 89 [Rn] 5f0
,6d0,7s2
.
+3
Thorium Th 90 [Rn] 5f0
,6d2,7s2
.
+2,+3,+4
Protoactinium Pa 91 [Rn] 5f2
,6d1,7s2
.
+3,+4,+5,
Uranium U 92 [Rn] 5f3
,6d1,7s2
.
+3,+4,+5,+6,
Neptunium Np 93 [Rn] 5f4
,6d1,7s2
.
+3,+4,+5,+6,+7
Plutonium Pu 94 [Rn] 5f6
,6d0,7s2
.
+3,+4,+5,+6,+7
Americium Am 95 [Rn] 5f7
,6d0,7s2
.
+2,+3,+4,+5,+6,
Curium Cm 96 [Rn] 5f7
,6d1,7s2
.
+3,+4
Berkellium Bk 97 [Rn] 5f9
,6d0,7s2
.
+3,+4
Californium Cf 98 [Rn] 5f10
,6d0,7s2
.
+2,+3
Einsteinnium Es 99 [Rn] 5f11
,6d0,7s2
.
+2,+3
Fermium Fm 100 [Rn] 5f12
,6d0,7s2
.
+2,+3
Mendelivium Md 101 [Rn] 5f13
,6d0,7s2
.
+2,+3
Nobelium No 102 [Rn] 5f14
,6d0,7s2
.
+2,+3
Lawrencium Lr 103 [Rn] 5f14
,6d1,7s2
.
+3

23. Ionic sizes
Magnetic properties are more complex than those of lanthanide.
Susceptibility is roughly parallel to the lanthanide.
Actinide contraction of trivalent ions is similar to that of
the lanthanides, and is caused again by the increasing
nuclear charge.
Magnetic properties

24. Physical and chemical reactivity
Silvery in appearance but display a variety of structures due
to the irregularity in metallic radii which are far greater
than are found in lanthanide.
Highly reactive metals, especially when finely divided.
Action of boiling water gives mixture of oxides and hydroxides.
Combination with most non-metals takes place at
moderate temperature.
HCl attacks all metals but most are slightly affected by HNO3
owing to the formation of protective oxide layers.

25. Comparison of Lanthanides and
Actinides
Similarities
Lanthanides and actinides involve filling of f-orbitals and
thus are similar in many respects.
The most common oxidation state is +3 for
both lanthanides and actinides.
Both are electropositive in nature
and thus very reactive.
Magnetic and spectral properties are
exhibited by both lanthanides and actinides.
Actinides exhibit actinide
contraction just like lanthanides.

26. Differences
Besides +3, lanthanides also show oxidation states of +2 and +4
while actinides show higher oxidation states of +4, +5, +6 and + 7
as well.
Lanthanide ions are colorless while most of the actinide ions
are coloured.
Actinides have a greater tendency towards complex formation
as compared to lanthanides.
Lanthanide compounds are less basic while actinide compounds
have appreciable basicity
Actinides form few important oxocations such as UO2
2+, PuO2
2+,
etc, while such oxocations are not known for lanthanides.
Almost all actinides are radioactive while lanthanides,
except promethium, are non-radioactive.
The magnetic properties of actinides can be easily explained
while it is difficult to do so in the case of lanthanides.

27. Thank you