LANTHANIDE
SALSABILA LATIFAH (2010412046)
Structur e and inorgani reactivit c
y
lanthanum
01
cerium
02
praseodymiu
03 m
neodymium
04
Gadolinium
05
TABEL OF
CONTENT
S
01
CHEMICAL AND
PHYSICAL PROPERTIES
02 COMPOUND
03 production
04 APPLICATION
Oxidation states
All lanthanides exhibit the most common and stable oxidation state of +3. This is because the sum of each lanthanide’s first three ionization energies is low,
allowing them to easily form their trivalent states. Other oxidation states +2 and +4 do exist for some lanthanides, however, they are less stable than +3. Hence oxidation state +2 and +4 occurs when they lead to
• noble gas configuartion e.g. Ce+4 (f0)
• a half-filled f-shell e.g. Eu2+ and Tb4+ (f7)
• a completely filled f-shell e.g. Yb2+ (f14)
Furthermore, elements that are near to these states also possess (+II) and (+IV) states. Examples: Sm2+ and Tm2+ have f6 and f13 arrangements, respectively, while Pr4+ and Nd4+ have f1 and f2 configurations.
Magnetic properties
Since the elements like La
3+and Ce
4+have noble gas configuration (f
0), and Lu
3+has a completely filled f-shell configuration (f
14), these elements are diamagnetic due to the absence of unpaired electrons. All other f states are paramagnetic as they have unpaired electrons.
The magnetic moment of the transition elements can be calculated by using the formula:
where, µ
(S+L)= magnetic moments in Bohr magnetons, S = resultant spin
quantum number, and L= resultant orbital momentum quantum number.
solubility
Many salts follow the pattern of group 2 elements in terms of solubility. Thus, chlorides and nitrates are soluble in
water, whereas oxalates, carbonates, and fluorides are not; however, suplhates are. Many lanthanides combine with group 1 or ammonium salts to form double salts.
Because these double salts crystallize well, they’ve been
utilized to separate the lanthanides.
57
La
Lanthanu
m
compounds
Lanthanum oxide is a white solid that can be prepared by direct
reaction of its constituent elements.
Due to the large size of the
La3+ ion, La2O3 adopts a hexagonal 7-coordinate structure
Lanthanum fluoride is insoluble in water and can be used as a qualitative test for the presence of La3+
The best characterized organolanthanum compounds are the cyclopentadienyl complex La(C5H5)3, which is
produced by reacting anhydrous LaCl3 with NaC5H5 in tetrahydrofuran
production
Lanthanum is the third-most abundant of all the lanthanides, making up 39 mg/kg of the Earth's crust, behind neodymium at 41.5 mg/kg and cerium at 66.5 mg/kg. It is almost three times as abundant as lead in the Earth's crust
Lanthanum metal is obtained from its oxide by heating it with ammonium chloride or fluoride and hydrofluoric acid at 300-400 °C to produce the chloride or fluoride:
La
2O
3+ 6 NH
4Cl → 2 LaCl
3+ 6 NH
3+ 3 H
2O
This is followed by reduction with alkali or alkaline earth metals in vacuum or argon atmosphere:
LaCl
3+ 3 Li → La + 3 LiCl
applications
LaB6 hot cathodec
One material used for anodic material of
nickel-metal hydride batterie s
is
La(Ni3.6Mn0.Al0.3Co0.7). Due to high cost to extract the other lanthanides, a mischmetal with more than 50% of
lanthanum is used instead of pure lanthanum.
Cerium-doped
lanthanum bromide and lanthanum chloride are the recent inorganic scintillators, which have a combination of high light yield, best energy resolution, and fast
response. Their high yield converts into superior energy resolution.
Carbon arc lamps use a mixture of rare earth
elements to improve the light quality. This application, especially by the
motion picture industry for studio lighting and
projection,
Cerium-doped lanthanum Carbon arc lamps
58
Ce
cerium
compounds
Cerium(IV) oxide,, is an oxide of the
rare-earth metal cerium. It is a pale yellow-white powder with the chemical formula CeO2.
Organocerium chemistry often involving complexes of cyclopentadienyl and cyclooctatetraenyl ligands. For example, Cerocene (Ce(C8H8)2)
production
applications
LaB6 hot cathodec
The photostability of
pigments can be enhanced by the addition of cerium, as it provides pigments with lightfastness and prevents clear polymers from
darkening in sunlight
Cerium salts, such as the sulfides Ce2S3 and Ce3S4, were considered during the Manhattan Project as
advanced
refractory materials for the construction of crucibles
as a catalytic converter for the oxidation of CO and NOx emissions in the exhaust gases from motor vehicles
Cerium-doped lanthanum Carbon arc lamps
59
Pr
Praseodymiu
m
compounds
Organopraseodymium compounds are very similar to those of the other lanthanides, as they all share an inability to undergo π backbonding. The
coordination chemistry of praseodymium is largely that of the large, electropositive Pr3+ ion
[Pr{N(SiMe3)2}3]
production
Praseodymium
• Monazite, because of its magnetic properties, can be separated by repeated electromagnetic separation.
• After separation, it is treated with hot concentrated sulfuric acid to produce water-soluble sulfates of rare earth.
• The acidic filtrates are partially neutralized with
sodium hydroxide to pH 3–4, during which thorium precipitates as hydroxide and is removed.
• The solution is treated with ammonium oxalate to convert rare earth to their insoluble oxalates, the oxalates are converted to oxides by annealing, and the oxides are dissolved in nitric acid.
• This last step excludes one of the main components, cerium,
whose oxide is insoluble in HNO
3.
applications
LaB6 hot cathodec
Praseodymium–nickel intermetallic (PrNi5) has such a strong
magnetocaloric effect that it has allowed scientists to approach within one
thousandth of a degree of absolute zero
Praseodymium is present in the rare-earth mixture whose fluoride forms the core of carbon arc lights, which are used in the
motion picture industry for studio lighting and projector lights.[
As an alloying agent with magnesium to create high- strength metals that are used in aircraft engines
Cerium-doped lanthanum Carbon arc lamps
60
Nd
Neodymiu
m
compounds
Some neodymium compounds have colors that vary based on the type of lighting
NdF3 Nd2O3
production
Neodymium is typically 10–18% of the rare-earth content of
commercial deposits of the light rare-earth-element minerals
bastnäsite and monazite.
applications
LaB6 hot cathodec
Neodymium has an unusually large specific
heat capacity at liquid-helium temperatures, so is useful in cryocoolers
Neodymium glass (Nd:glass) is produced by the inclusion of neodymium oxide (Nd2O3) in the glass melt. Usually in daylight or incandescent light neodymium glass appears lavender, but it appears pale blue under fluorescent
lighting.
Uranyl acetate has been the standard contrasting agent in transmission
electron microscopy (TEM) for decades.[80][81] However, its use is increasingly
hampered by regulations by governments due to its
radioactive properties as well as its high toxicity.
Cerium-doped lanthanum Carbon arc lamps
64
Gd
Gadoliniu
m
compounds
gadolinium adopts the oxidation state +3. However, gadolinium can be found on rare occasions in the 0, +1 and +2 oxidation states. Most commonly encountered of the halides is gadolinium(III) chloride (GdCl3).
Gadolinium(III), like most lanthanide ions, forms complexes with high coordination numbers. This tendency is illustrated by the use of the chelating agent DOTA, an octadentate ligand
production
Gadolinium is produced both from monazite and bastnäsite.
1. Crushed minerals are extracted with hydrochloric acid or sulfuric acid, which converts the insoluble oxides into soluble chlorides or sulfates.
2. The acidic filtrates are partially neutralized with caustic soda to pH 3–4. Thorium precipitates as its hydroxide, and is then removed.
3. The remaining solution is treated with ammonium oxalate to convert rare earths into their insoluble oxalates. The oxalates are converted to oxides by heating.
4. The oxides are dissolved in nitric acid that excludes one of the main components, cerium, whose oxide is insoluble in HNO
3.
5. The solution is treated with magnesium nitrate to produce a crystallized mixture of double salts of gadolinium, samarium and europium.
6. The salts are separated by ion exchange chromatography.
7. The rare-earth ions are then selectively washed out by a suitable complexing
agent.
applications
LaB6 hot cathodec
In X-ray systems gadolinium is contained in the phosphor layer, suspended in a
polymer matrix at the detector. Terbium-doped gadolinium oxysulfide (Gd2O2S:Tb) at the
phosphor layer converts the X-rays released from the source into light.
Gadolinium can also serve as an electrolyte in
solid oxide fuel cells (SOFCs). It creates an electrolyte with both high ionic conductivity and low operating temperatures, which are optimal for cost- effective production of fuel cells.
Gadolinium-based materials, such as Gd5(SixGe1−x)4, are currently the most promising materials, owing to their high Curie temperature and giant magnetocaloric effect.
Cerium-doped lanthanum Carbon arc lamps
