Gadolinium is silvery white, has a metallic luster, and is is malleable
(capable of being extended or shaped by beating with a hammer or by the
pressure of rollers) and ductile (capable of being drawn out into wire or
threads). It is ferromagnetic (strongly attracted by a magnet).
The metal is relatively stable in dry air, but in moist air it tarnishes with the formation of a loosely adhering oxide film which "spalls"
off and exposes more surface to oxidation. The metal reacts slowly with water
and is soluble in dilute acid. Gadolinium has the highest thermal neutron
capture cross-section of any known element.
•Name: Gadolinium
•Symbol: Gd
•Atomic number: 64
•Atomic weight: 157.25 (3)
[see note g]
•Standard state: solid at
298 K
•CAS Registry ID: 7440-54-2
•Group in periodic table:
•Group name: Lanthanoid
•Period in periodic table:
6 (lanthanoid)
•Block in periodic table:
f-block
•Color: silvery white
•Classification: Metallic
Historical information
Gadolinium was discovered
by Jean de Marignac at 1880 in Switzerland, and named for J.
"Gadolin", a Finnish chemist and minerologist. Spectroscopic lines
due to gadolinium were observed in samples of didymia and gadolinite.
Gadolinia, the oxide of gadolinium, was separated by Paul-Emile Loq de
Biosbaudran in 1886. The element was named for the mineral gadolinite from
which this rare earth was originally obtained. The element itself was isolated
only recently.
Physical properties
•Melting point: 1585 [or
1312 °C (2394 °F)] K
•Boiling point: 3523 [or
3250 °C (5882 °F)] K
•Density of solid: 7901 kg
m-3
Orbital properties
•Ground state electron
configuration: [Xe].4f7.5d1.6s2
•Shell structure:
2.8.18.25.9.2
•Term symbol: 9D2
Isolation
Gadolinium metal is
available commercially so it is not normally necessary to make it in the
laboratory, which is just as well as it is difficult to isolate as the pure
metal. This is largely because of the way it is found in nature. The
lanthanoids are found in nature in a number of minerals. The most important are
xenotime, monazite, and bastnaesite. The first two are orthophosphate minerals
LnPO4 (Ln deonotes a mixture of all the lanthanoids except promethium which is
vanishingly rare) and the third is a fluoride carbonate LnCO3F. Lanthanoids
with even atomic numbers are more common. The most comon lanthanoids in these
minerals are, in order, cerium, lanthanum, neodymium, and praseodymium.
Monazite also contains thorium and ytrrium which makes handling difficult since
thorium and its decomposition products are radioactive.
For many purposes it is not
particularly necessary to separate the metals, but if separation into
individual metals is required, the process is complex. Initially, the metals
are extracted as salts from the ores by extraction with sulphuric acid (H2SO4),
hydrochloric acid (HCl), and sodium hydroxide (NaOH). Modern purification
techniques for these lanthanoid salt mixtures are ingenious and involve
selective complexation techniques, solvent extractions, and ion exchange
chromatography.
Pure gadolinium is
available through the reduction of GdF3 with calcium metal.
2GdF3 + 3Ca → 2Gd + 3CaF2
This would work for the
other calcium halides as well but the product CaF2 is easier to handle under
the reaction conditions (heat to 50°C above the melting point of the element in
an argon atmosphere). Excess calcium is removed from the reaction mixture under
vacuum.
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Thursday, October 31, 2013
Monday, October 28, 2013
Europium (63)
Europium ignites in air at about 150 to 180°C. Europium is
about as hard as lead and is quite ductile. It is the most reactive of the rare
earth metals, quickly oxidising in air. It resembles calcium in its reaction
with water. It is used in television screens to produce a red colour.
•Name: Europium
•Symbol: Eu
•Atomic number: 63
•Atomic weight: 151.964 (1) [see note g]
•Standard state: solid at 298 K
•CAS Registry ID: 7440-53-1
•Group in periodic table:
•Group name: Lanthanoid
•Period in periodic table: 6 (lanthanoid)
•Block in periodic table: f-block
•Color: silvery white
•Classification: Metallic
Historical information
Origin of name (betcha could've guessed this one!)- named after "Europe". The discovery of europium is generally credited to Eugene-Antole Demarcay, who separated the earth in reasonably pure form in 1901 from a material containing largely samarium. Pure europium metal was not isolated until much more recently.
Physical properties
•Melting point: 1099 [or 826 °C (1519 °F)] K
•Boiling point: 1800 [or 1527 °C (2781 °F)] K
•Density of solid: 5244 kg m-3
Orbital properties
•Ground state electron configuration: [Xe].4f7.6s2
•Shell structure: 2.8.18.25.8.2
•Term symbol: 8S7/2
Isolation
Europium metal is available commercially so it is not normally necessary to make it in the laboratory, which is just as well as it is difficult to isolate as the pure metal. This is largely because of the way it is found in nature. The lanthanoids are found in nature in a number of minerals. The most important are xenotime, monazite, and bastnaesite. The first two are orthophosphate minerals LnPO4 (Ln deonotes a mixture of all the lanthanoids except promethium which is vanishingly rare) and the third is a fluoride carbonate LnCO3F. Lanthanoids with even atomic numbers are more common. The most comon lanthanoids in these minerals are, in order, cerium, lanthanum, neodymium, and praseodymium. Monazite also contains thorium and ytrrium which makes handling difficult since thorium and its decomposition products are radioactive.
For many purposes it is not particularly necessary to separate the metals, but if separation into individual metals is required, the process is complex. Initially, the metals are extracted as salts from the ores by extraction with sulphuric acid (H2SO4), hydrochloric acid (HCl), and sodium hydroxide (NaOH). Modern purification techniques for these lanthanoid salt mixtures are ingenious and involve selective complexation techniques, solvent extractions, and ion exchange chromatography.
Pure europium is available through the electrolysis of a mixture of molten EuCl3 and NaCl (or CaCl2) in a graphite cell which acts as cathode using graphite as anode. The other product is chlorine gas.
•Name: Europium
•Symbol: Eu
•Atomic number: 63
•Atomic weight: 151.964 (1) [see note g]
•Standard state: solid at 298 K
•CAS Registry ID: 7440-53-1
•Group in periodic table:
•Group name: Lanthanoid
•Period in periodic table: 6 (lanthanoid)
•Block in periodic table: f-block
•Color: silvery white
•Classification: Metallic
Historical information
Origin of name (betcha could've guessed this one!)- named after "Europe". The discovery of europium is generally credited to Eugene-Antole Demarcay, who separated the earth in reasonably pure form in 1901 from a material containing largely samarium. Pure europium metal was not isolated until much more recently.
Physical properties
•Melting point: 1099 [or 826 °C (1519 °F)] K
•Boiling point: 1800 [or 1527 °C (2781 °F)] K
•Density of solid: 5244 kg m-3
Orbital properties
•Ground state electron configuration: [Xe].4f7.6s2
•Shell structure: 2.8.18.25.8.2
•Term symbol: 8S7/2
Isolation
Europium metal is available commercially so it is not normally necessary to make it in the laboratory, which is just as well as it is difficult to isolate as the pure metal. This is largely because of the way it is found in nature. The lanthanoids are found in nature in a number of minerals. The most important are xenotime, monazite, and bastnaesite. The first two are orthophosphate minerals LnPO4 (Ln deonotes a mixture of all the lanthanoids except promethium which is vanishingly rare) and the third is a fluoride carbonate LnCO3F. Lanthanoids with even atomic numbers are more common. The most comon lanthanoids in these minerals are, in order, cerium, lanthanum, neodymium, and praseodymium. Monazite also contains thorium and ytrrium which makes handling difficult since thorium and its decomposition products are radioactive.
For many purposes it is not particularly necessary to separate the metals, but if separation into individual metals is required, the process is complex. Initially, the metals are extracted as salts from the ores by extraction with sulphuric acid (H2SO4), hydrochloric acid (HCl), and sodium hydroxide (NaOH). Modern purification techniques for these lanthanoid salt mixtures are ingenious and involve selective complexation techniques, solvent extractions, and ion exchange chromatography.
Pure europium is available through the electrolysis of a mixture of molten EuCl3 and NaCl (or CaCl2) in a graphite cell which acts as cathode using graphite as anode. The other product is chlorine gas.
Thursday, October 24, 2013
Samarium (62)
Samarium has a bright silver lustre and is reasonably stable
in air. It ignites in air at 150°C. It is a rare earth metal. It is found with
other rare earth elements in minerals including monazite and bastnaesite and is
used in electronics industries.
•Name: Samarium
•Symbol: Sm
•Atomic number: 62
•Atomic weight: 150.36 (2) [see note g]
•Standard state: solid at 298 K
•CAS Registry ID: 7440-19-9
•Group in periodic table:
•Group name: Lanthanoid
•Period in periodic table: 6 (lanthanoid)
•Block in periodic table: f-block
•Color: silvery white
•Classification: Metallic
Historical information
Samarium was discovered by Paul Emile Lecoq de Boisbaudran at 1879 in France. The element was isolated in 1879 by Lecoq de Boisbaudran from the mineral samarskite, named in honour of a Russian mine official, Colonel Samarski, and which therefore gave samarium its name. Samarium was discovered spectroscopically by its sharp absorption lines in 1853 by Jean Charles Galissard de Marignac in an "earth" called didymia.
Physical properties
•Melting point: 1345 [or 1072 °C (1962 °F)] K
•Boiling point: 2076 [or 1803 °C (3277 °F)] K
•Density of solid: 7353 kg m-3
Oorbital properties
•Ground state electron configuration: [Xe].4f6.6s2
•Shell structure: 2.8.18.24.8.2
•Term symbol: 7F0
Isolation
Samarium metal is available commercially so it is not normally necessary to make it in the laboratory, which is just as well as it is difficult to isolate as the pure metal. This is largely because of the way it is found in nature. The lanthanoids are found in nature in a number of minerals. The most important are xenotime, monazite, and bastnaesite. The first two are orthophosphate minerals LnPO4 (Ln deonotes a mixture of all the lanthanoids except promethium which is vanishingly rare) and the third is a fluoride carbonate LnCO3F. Lanthanoids with even atomic numbers are more common. The most comon lanthanoids in these minerals are, in order, cerium, lanthanum, neodymium, and praseodymium. Monazite also contains thorium and ytrrium which makes handling difficult since thorium and its decomposition products are radioactive.
For many purposes it is not particularly necessary to separate the metals, but if separation into individual metals is required, the process is complex. Initially, the metals are extracted as salts from the ores by extraction with sulphuric acid (H2SO4), hydrochloric acid (HCl), and sodium hydroxide (NaOH). Modern purification techniques for these lanthanoid salt mixtures are ingenious and involve selective complexation techniques, solvent extractions, and ion exchange chromatography.
Pure samarium is available through the electrolysis of a mixture of molten SmCl3 and NaCl (or CaCl2) in a graphite cell which acts as cathode using graphite as anode. The other product is chlorine gas.
•Name: Samarium
•Symbol: Sm
•Atomic number: 62
•Atomic weight: 150.36 (2) [see note g]
•Standard state: solid at 298 K
•CAS Registry ID: 7440-19-9
•Group in periodic table:
•Group name: Lanthanoid
•Period in periodic table: 6 (lanthanoid)
•Block in periodic table: f-block
•Color: silvery white
•Classification: Metallic
Historical information
Samarium was discovered by Paul Emile Lecoq de Boisbaudran at 1879 in France. The element was isolated in 1879 by Lecoq de Boisbaudran from the mineral samarskite, named in honour of a Russian mine official, Colonel Samarski, and which therefore gave samarium its name. Samarium was discovered spectroscopically by its sharp absorption lines in 1853 by Jean Charles Galissard de Marignac in an "earth" called didymia.
Physical properties
•Melting point: 1345 [or 1072 °C (1962 °F)] K
•Boiling point: 2076 [or 1803 °C (3277 °F)] K
•Density of solid: 7353 kg m-3
Oorbital properties
•Ground state electron configuration: [Xe].4f6.6s2
•Shell structure: 2.8.18.24.8.2
•Term symbol: 7F0
Isolation
Samarium metal is available commercially so it is not normally necessary to make it in the laboratory, which is just as well as it is difficult to isolate as the pure metal. This is largely because of the way it is found in nature. The lanthanoids are found in nature in a number of minerals. The most important are xenotime, monazite, and bastnaesite. The first two are orthophosphate minerals LnPO4 (Ln deonotes a mixture of all the lanthanoids except promethium which is vanishingly rare) and the third is a fluoride carbonate LnCO3F. Lanthanoids with even atomic numbers are more common. The most comon lanthanoids in these minerals are, in order, cerium, lanthanum, neodymium, and praseodymium. Monazite also contains thorium and ytrrium which makes handling difficult since thorium and its decomposition products are radioactive.
For many purposes it is not particularly necessary to separate the metals, but if separation into individual metals is required, the process is complex. Initially, the metals are extracted as salts from the ores by extraction with sulphuric acid (H2SO4), hydrochloric acid (HCl), and sodium hydroxide (NaOH). Modern purification techniques for these lanthanoid salt mixtures are ingenious and involve selective complexation techniques, solvent extractions, and ion exchange chromatography.
Pure samarium is available through the electrolysis of a mixture of molten SmCl3 and NaCl (or CaCl2) in a graphite cell which acts as cathode using graphite as anode. The other product is chlorine gas.
Monday, October 21, 2013
Promethium (61)
PROMETHIUM [PRO-ME-THE-UM]
And no, it has nothing to do with that poor movie trying to be a prequel to ALIEN.
The essentials
Great care is required while handling promethium as a consequence of its radioactivity. Promethium salts luminesce in the dark with a pale blue or greenish glow, due to their high radioactivity. Ion-exchange methods led to the preparation of about 10 g of promethium from atomic reactor fuel processing wastes in early 1963.
Little is yet generally known about the properties of metallic promethium. More than 30 promethium compounds have been prepared. Promethium is a rare earth metal. It appears that there is no known Pm existing in the earth's crust.
•Name: Promethium
•Symbol: Pm
•Atomic number: 61
•Atomic weight: [ 145 ]
•Standard state: solid at 298 K
•CAS Registry ID: 7440-12-2
•Group in periodic table:
•Group name: Lanthanoid
•Period in periodic table: 6 (lanthanoid)
•Block in periodic table: f-block
•Colour: metallic
•Classification: Metallic
Historical information
Promethium was discovered by J. A. Marinsky, Lawrence Glendenin, Charles D. Coryell at 1945 in United States. Origin of name: named after "Prometheus" in Greek mythology, who stole fire from the gods. Early claims to the discovery of promethium date back to 1924 but these appear have been substantiated. A group at Ohio State University (USA) claimed element 61 in experiments involving its synthesis in a cyclotron, but again the evidence did not satisfy everyone. In 1947, Marinsky, Glendenin, and Coryell at Oak Ridge, Tennessee, USA, made the first chemical identification of promethium by use of ion-exchange chromatography on residues in a nuclear reactor.
Physical properties
•Melting point: 1373 [or 1100 °C (2012 °F)] K
•Boiling point: 3273 [or 3000 °C (5432 °F)] K
•Density of solid: 7264 kg m-3
Orbital properties
•Ground state electron configuration: [Xe].4f5.6s2
•Shell structure: 2.8.18.23.8.2
•Term symbol: 6H5/2
Isolation
Promethium metal is available commercially so it is not normally necessary to make it in the laboratory, which is just as well as it is difficult to isolate as the pure metal. This is largely because of the way it is found in nature. The lanthanoids are found in nature in a number of minerals. The most important are xenotime, monazite, and bastnaesite. The first two are orthophosphate minerals LnPO4 (Ln deonotes a mixture of all the lanthanoids except promethium which is vanishingly rare) and the third is a fluoride carbonate LnCO3F. Lanthanoids with even atomic numbers are more common. The most comon lanthanoids in these minerals are, in order, cerium, lanthanum, neodymium, and praseodymium. Monazite also contains thorium and ytrrium which makes handling difficult since thorium and its decomposition products are radioactive.
For many purposes it is not particularly necessary to separate the metals, but if separation into individual metals is required, the process is complex. Initially, the metals are extracted as salts from the ores by extraction with sulphuric acid (H2SO4), hydrochloric acid (HCl), and sodium hydroxide (NaOH). Modern purification techniques for these lanthanoid salt mixtures are ingenious and involve selective complexation techniques, solvent extractions, and ion exchange chromatography.
Pure promethium is available through the reduction of PmF3 with calcium metal.
2PmF3 + 3Ca → 2Pm + 3CaF2
This would work for the other calcium halides as well but the product CaF2 is easier to handle under the reaction conditions (heat to 50°C above the melting point of the element in an argon atmosphere). Excess calcium is removed from the reaction mixture under vacuum.
And no, it has nothing to do with that poor movie trying to be a prequel to ALIEN.
The essentials
Great care is required while handling promethium as a consequence of its radioactivity. Promethium salts luminesce in the dark with a pale blue or greenish glow, due to their high radioactivity. Ion-exchange methods led to the preparation of about 10 g of promethium from atomic reactor fuel processing wastes in early 1963.
Little is yet generally known about the properties of metallic promethium. More than 30 promethium compounds have been prepared. Promethium is a rare earth metal. It appears that there is no known Pm existing in the earth's crust.
•Name: Promethium
•Symbol: Pm
•Atomic number: 61
•Atomic weight: [ 145 ]
•Standard state: solid at 298 K
•CAS Registry ID: 7440-12-2
•Group in periodic table:
•Group name: Lanthanoid
•Period in periodic table: 6 (lanthanoid)
•Block in periodic table: f-block
•Colour: metallic
•Classification: Metallic
Historical information
Promethium was discovered by J. A. Marinsky, Lawrence Glendenin, Charles D. Coryell at 1945 in United States. Origin of name: named after "Prometheus" in Greek mythology, who stole fire from the gods. Early claims to the discovery of promethium date back to 1924 but these appear have been substantiated. A group at Ohio State University (USA) claimed element 61 in experiments involving its synthesis in a cyclotron, but again the evidence did not satisfy everyone. In 1947, Marinsky, Glendenin, and Coryell at Oak Ridge, Tennessee, USA, made the first chemical identification of promethium by use of ion-exchange chromatography on residues in a nuclear reactor.
Physical properties
•Melting point: 1373 [or 1100 °C (2012 °F)] K
•Boiling point: 3273 [or 3000 °C (5432 °F)] K
•Density of solid: 7264 kg m-3
Orbital properties
•Ground state electron configuration: [Xe].4f5.6s2
•Shell structure: 2.8.18.23.8.2
•Term symbol: 6H5/2
Isolation
Promethium metal is available commercially so it is not normally necessary to make it in the laboratory, which is just as well as it is difficult to isolate as the pure metal. This is largely because of the way it is found in nature. The lanthanoids are found in nature in a number of minerals. The most important are xenotime, monazite, and bastnaesite. The first two are orthophosphate minerals LnPO4 (Ln deonotes a mixture of all the lanthanoids except promethium which is vanishingly rare) and the third is a fluoride carbonate LnCO3F. Lanthanoids with even atomic numbers are more common. The most comon lanthanoids in these minerals are, in order, cerium, lanthanum, neodymium, and praseodymium. Monazite also contains thorium and ytrrium which makes handling difficult since thorium and its decomposition products are radioactive.
For many purposes it is not particularly necessary to separate the metals, but if separation into individual metals is required, the process is complex. Initially, the metals are extracted as salts from the ores by extraction with sulphuric acid (H2SO4), hydrochloric acid (HCl), and sodium hydroxide (NaOH). Modern purification techniques for these lanthanoid salt mixtures are ingenious and involve selective complexation techniques, solvent extractions, and ion exchange chromatography.
Pure promethium is available through the reduction of PmF3 with calcium metal.
2PmF3 + 3Ca → 2Pm + 3CaF2
This would work for the other calcium halides as well but the product CaF2 is easier to handle under the reaction conditions (heat to 50°C above the melting point of the element in an argon atmosphere). Excess calcium is removed from the reaction mixture under vacuum.
Thursday, October 17, 2013
Neodymium (60)
Neodymium [KNEE-OH-DIM-EE-UM] is present in misch metal (an
alloy of rare earth elements in various naturally occurring proportions) to the
extent of about 18%. The metal has a bright silvery metallic lustre. Neodymium
is one of the more reactive rare-earth metals and quickly tarnishes in air,
forming an oxide that spalls off and exposes the metal to further oxidation. It
is one of the rare earth metals.
•Name: Neodymium
•Symbol: Nd
•Atomic number: 60
•Atomic weight: 144.242 (3) [see note g]
•Standard state: solid at 298 K
•CAS Registry ID: 7440-00-8
•Group in periodic table:
•Group name: Lanthanoid
•Period in periodic table: 6 (lanthanoid)
•Block in periodic table: f-block
•Color: silvery white, yellowish tinge
•Classification: Metallic
Historical information
Neodymium was discovered by Carl F. Auer von Welsbach at 1885 in Austria. Von Welsbach separated didymium, an extract of cerite, into two new elemental components, neodymia and praseodymia, by repeated fractionation of ammonium didymium nitrate. Origin of name: from the Greek words "neos didymos" meaning "new twin". While the free metal is a component of misch metal, (a pyrophoric alloy for lighter flints), the element was not isolated in relatively pure form until 1925.
Physical properties
•Melting point: 1297 [or 1024 °C (1875 °F)] K
•Boiling point: 3373 [or 3100 °C (5612 °F)] K
•Density of solid: 6800 kg m-3
Orbital properties
•Ground state electron configuration: [Xe].4f4.6s2
•Shell structure: 2.8.18.22.8.2
•Term symbol: 5I4
Isolation
Neodymium metal is available commercially so it is not normally necessary to make it in the laboratory, which is just as well as it is difficult to isolate as the pure metal. This is largely because of the way it is found in nature. The lanthanoids are found in nature in a number of minerals. The most important are xenotime, monazite, and bastnaesite. The first two are orthophosphate minerals LnPO4 (Ln deonotes a mixture of all the lanthanoids except promethium which is vanishingly rare) and the third is a fluoride carbonate LnCO3F. Lanthanoids with even atomic numbers are more common. The most comon lanthanoids in these minerals are, in order, cerium, lanthanum, neodymium, and praseodymium. Monazite also contains thorium and ytrrium which makes handling difficult since thorium and its decomposition products are radioactive.
For many purposes it is not particularly necessary to separate the metals, but if separation into individual metals is required, the process is complex. Initially, the metals are extracted as salts from the ores by extraction with sulphuric acid (H2SO4), hydrochloric acid (HCl), and sodium hydroxide (NaOH). Modern purification techniques for these lanthanoid salt mixtures are ingenious and involve selective complexation techniques, solvent extractions, and ion exchange chromatography.
Pure neodymium is available through the reduction of NdF3 with calcium metal.
2NdF3 + 3Ca → 2Nd + 3CaF2
This would work for the other calcium halides as well but the product CaF2 is easier to handle under the reaction conditions (heat to 50°C above the melting point of the element in an argon atmosphere). Excess calcium is removed from the reaction mixture under vacuum.
•Name: Neodymium
•Symbol: Nd
•Atomic number: 60
•Atomic weight: 144.242 (3) [see note g]
•Standard state: solid at 298 K
•CAS Registry ID: 7440-00-8
•Group in periodic table:
•Group name: Lanthanoid
•Period in periodic table: 6 (lanthanoid)
•Block in periodic table: f-block
•Color: silvery white, yellowish tinge
•Classification: Metallic
Historical information
Neodymium was discovered by Carl F. Auer von Welsbach at 1885 in Austria. Von Welsbach separated didymium, an extract of cerite, into two new elemental components, neodymia and praseodymia, by repeated fractionation of ammonium didymium nitrate. Origin of name: from the Greek words "neos didymos" meaning "new twin". While the free metal is a component of misch metal, (a pyrophoric alloy for lighter flints), the element was not isolated in relatively pure form until 1925.
Physical properties
•Melting point: 1297 [or 1024 °C (1875 °F)] K
•Boiling point: 3373 [or 3100 °C (5612 °F)] K
•Density of solid: 6800 kg m-3
Orbital properties
•Ground state electron configuration: [Xe].4f4.6s2
•Shell structure: 2.8.18.22.8.2
•Term symbol: 5I4
Isolation
Neodymium metal is available commercially so it is not normally necessary to make it in the laboratory, which is just as well as it is difficult to isolate as the pure metal. This is largely because of the way it is found in nature. The lanthanoids are found in nature in a number of minerals. The most important are xenotime, monazite, and bastnaesite. The first two are orthophosphate minerals LnPO4 (Ln deonotes a mixture of all the lanthanoids except promethium which is vanishingly rare) and the third is a fluoride carbonate LnCO3F. Lanthanoids with even atomic numbers are more common. The most comon lanthanoids in these minerals are, in order, cerium, lanthanum, neodymium, and praseodymium. Monazite also contains thorium and ytrrium which makes handling difficult since thorium and its decomposition products are radioactive.
For many purposes it is not particularly necessary to separate the metals, but if separation into individual metals is required, the process is complex. Initially, the metals are extracted as salts from the ores by extraction with sulphuric acid (H2SO4), hydrochloric acid (HCl), and sodium hydroxide (NaOH). Modern purification techniques for these lanthanoid salt mixtures are ingenious and involve selective complexation techniques, solvent extractions, and ion exchange chromatography.
Pure neodymium is available through the reduction of NdF3 with calcium metal.
2NdF3 + 3Ca → 2Nd + 3CaF2
This would work for the other calcium halides as well but the product CaF2 is easier to handle under the reaction conditions (heat to 50°C above the melting point of the element in an argon atmosphere). Excess calcium is removed from the reaction mixture under vacuum.
Monday, October 14, 2013
Praseodymium (59)
Praseodymium [PRAY-SEE-OH-DIM-EE-UM] is soft, silvery,
malleable, and ductile. It was prepared in relatively pure form in 1931. It is
somewhat more resistant to corrosion in air than europium, lanthanum, cerium,
or neodymium, but it does develop a green oxide coating that "spalls"
away when exposed to air. The metal should be stored under an inert atmosphere
or under mineral oil or petroleum.
The rare-earth oxides, including Pr2O3, are among the most refractory substances known. It is a component of misch metal, used for lighter flints, and of the glass in welders' goggles.
•Name: Praseodymium
•Symbol: Pr
•Atomic number: 59
•Atomic weight: 140.90765 (2)
•Standard state: solid at 298 K
•CAS Registry ID: 7440-10-0
•Group in periodic table:
•Group name: Lanthanoid
•Period in periodic table: 6 (lanthanoid)
•Block in periodic table: f-block
•Color: silvery white, yellowish tinge
•Classification: Metallic
Historical information
Praseodymium was discovered by Carl F. Auer von Welsbach at 1885 in Austria. Carl Auer von Welsbach separated an "earth" called didymia obtained from the mineral samarskite into two earths, praseodymia and neodymia, which gave salts of different colours. The separation required the repeated fractionation of ammonium didymium nitrate. Origin of name: from the Greek words "prasios didymos" meaning "green twin".
Physical properties
•Melting point: 1208 [or 935 °C (1715 °F)] K
•Boiling point: 3563 [or 3290 °C (5954 °F)] K
•Density of solid: 6640 kg m-3
Praseodymium: orbital properties
•Ground state electron configuration: [Xe].4f3.6s2
•Shell structure: 2.8.18.21.8.2
•Term symbol: 4I9/2
Isolation
Praseodymium metal is available commercially so it is not normally necessary to make it in the laboratory, which is just as well as it is difficult to isolate as the pure metal. This is largely because of the way it is found in nature. The lanthanoids are found in nature in a number of minerals. The most important are xenotime, monazite, and bastnaesite. The first two are orthophosphate minerals LnPO4 (Ln deonotes a mixture of all the lanthanoids except promethium which is vanishingly rare) and the third is a fluoride carbonate LnCO3F. Lanthanoids with even atomic numbers are more common. The most comon lanthanoids in these minerals are, in order, cerium, lanthanum, neodymium, and praseodymium. Monazite also contains thorium and ytrrium which makes handling difficult since thorium and its decomposition products are radioactive.
For many purposes it is not particularly necessary to separate the metals, but if separation into individual metals is required, the process is complex. Initially, the metals are extracted as salts from the ores by extraction with sulphuric acid (H2SO4), hydrochloric acid (HCl), and sodium hydroxide (NaOH). Modern purification techniques for these lanthanoid salt mixtures are ingenious and involve selective complexation techniques, solvent extractions, and ion exchange chromatography.
Pure praseodymium is available through the reduction of PrF3 with calcium metal.
2PrF3 + 3Ca → 2Pr + 3CaF2
This would work for the other calcium halides as well but the product CaF2 is easier to handle under the reaction conditions (heat to 50°C above the melting point of the element in an argon atmosphere). Excess calcium is removed from the reaction mixture under vacuum.
The rare-earth oxides, including Pr2O3, are among the most refractory substances known. It is a component of misch metal, used for lighter flints, and of the glass in welders' goggles.
•Name: Praseodymium
•Symbol: Pr
•Atomic number: 59
•Atomic weight: 140.90765 (2)
•Standard state: solid at 298 K
•CAS Registry ID: 7440-10-0
•Group in periodic table:
•Group name: Lanthanoid
•Period in periodic table: 6 (lanthanoid)
•Block in periodic table: f-block
•Color: silvery white, yellowish tinge
•Classification: Metallic
Historical information
Praseodymium was discovered by Carl F. Auer von Welsbach at 1885 in Austria. Carl Auer von Welsbach separated an "earth" called didymia obtained from the mineral samarskite into two earths, praseodymia and neodymia, which gave salts of different colours. The separation required the repeated fractionation of ammonium didymium nitrate. Origin of name: from the Greek words "prasios didymos" meaning "green twin".
Physical properties
•Melting point: 1208 [or 935 °C (1715 °F)] K
•Boiling point: 3563 [or 3290 °C (5954 °F)] K
•Density of solid: 6640 kg m-3
Praseodymium: orbital properties
•Ground state electron configuration: [Xe].4f3.6s2
•Shell structure: 2.8.18.21.8.2
•Term symbol: 4I9/2
Isolation
Praseodymium metal is available commercially so it is not normally necessary to make it in the laboratory, which is just as well as it is difficult to isolate as the pure metal. This is largely because of the way it is found in nature. The lanthanoids are found in nature in a number of minerals. The most important are xenotime, monazite, and bastnaesite. The first two are orthophosphate minerals LnPO4 (Ln deonotes a mixture of all the lanthanoids except promethium which is vanishingly rare) and the third is a fluoride carbonate LnCO3F. Lanthanoids with even atomic numbers are more common. The most comon lanthanoids in these minerals are, in order, cerium, lanthanum, neodymium, and praseodymium. Monazite also contains thorium and ytrrium which makes handling difficult since thorium and its decomposition products are radioactive.
For many purposes it is not particularly necessary to separate the metals, but if separation into individual metals is required, the process is complex. Initially, the metals are extracted as salts from the ores by extraction with sulphuric acid (H2SO4), hydrochloric acid (HCl), and sodium hydroxide (NaOH). Modern purification techniques for these lanthanoid salt mixtures are ingenious and involve selective complexation techniques, solvent extractions, and ion exchange chromatography.
Pure praseodymium is available through the reduction of PrF3 with calcium metal.
2PrF3 + 3Ca → 2Pr + 3CaF2
This would work for the other calcium halides as well but the product CaF2 is easier to handle under the reaction conditions (heat to 50°C above the melting point of the element in an argon atmosphere). Excess calcium is removed from the reaction mixture under vacuum.
Thursday, October 10, 2013
Cerium (58)
Metallic cerium is prepared by reduction techniques, such as
by reducing cerous fluoride with calcium, or by electrolysis of molten cerous
chloride or other cerous halides.
Cerium is an iron-grey lustrous metal. It is malleable, and oxidises very readily at room temperature, especially in moist air. Except for europium, cerium is the most reactive of the rare-earth metals. It slowly decomposes in cold water, and rapidly in hot water. Alkali solutions and dilute and concentrated acids attack the metal rapidly. The pure metal may ignite when scratched with a knife. It reacts with all of the halides (F, Cl, Br, I)
It is the most abundant of the rare earth metals and is found in minerals including allanite, monazite, cerite, and bastnaesite. There are large deposits found in India, Brazil and the USA.
•Name: Cerium
•Symbol: Ce
•Atomic number: 58
•Atomic weight: 140.116 (1) [see note g]
•Standard state: solid at 298 K
•CAS Registry ID: 7440-45-1
•Group in periodic table:
•Group name: Lanthanoid
•Period in periodic table: 6 (lanthanoid)
•Block in periodic table: f-block
•Color: silvery white
•Classification: Metallic
Historical information
Cerium was discovered by Wilhelm von Hisinger, Jöns Jacob Berzelius, Martin Klaproth at 1803 in Sweden, and independently by Maratin Klparothe, Germany. Cerium was named by Berzelius after the dwarf planet Ceres, discovered two years earlier (1801) Ceres, which was itself named for the Roman goddess of agriculture. It was isolated from a mineral from an iron mine at Bastnas.
Physical properties
•Melting point: 1068 [or 795 °C (1463 °F)] K
•Boiling point: 3633 [or 3360 °C (6080 °F)] K
•Density of solid: 6689 kg m-3
Orbital properties
•Ground state electron configuration: [Xe].4f1.5d1.6s2
•Shell structure: 2.8.18.19.9.2
•Term symbol: 1G4
Isolation
Cerium metal is available commercially so it is not normally necessary to make it in the laboratory, which is just as well as it is difficult to isolate as the pure metal. This is largely because of the way it is found in nature. The lanthanoids are found in nature in a number of minerals. The most important are xenotime, monazite, and bastnaesite. The first two are orthophosphate minerals LnPO4 (Ln deonotes a mixture of all the lanthanoids except promethium which is vanishingly rare) and the third is a fluoride carbonate LnCO3F. Lanthanoids with even atomic numbers are more common. The most comon lanthanoids in these minerals are, in order, cerium, lanthanum, neodymium, and praseodymium. Monazite also contains thorium and ytrrium which makes handling difficult since thorium and its decomposition products are radioactive.
For many purposes it is not particularly necessary to separate the metals, but if separation into individual metals is required, the process is complex. Initially, the metals are extracted as salts from the ores by extraction with sulphuric acid (H2SO4), hydrochloric acid (HCl), and sodium hydroxide (NaOH). The ceric ion, Ce(IV) is more easily hydrolysed than the lanthanide (III) ions and therefore precipitates as a salt upon treatment with an oxidizing agent such as KMnO4.
Pure cerium is available through the electrolysis of a mixture of molten CeCl3 and NaCl (or CaCl2) in a graphite cell which acts as cathode using graphite as anode. The other product is chlorine gas.
Cerium, like all rare-earth metals, is of low to moderate toxicity. Cerium is a strong reducing agent and ignites spontaneously in air at 65 to 80 °C. Fumes from cerium fires are toxic. Water should not be used to stop cerium fires, as cerium reacts with water to produce hydrogen gas. Workers exposed to cerium have experienced itching, sensitivity to heat, and skin lesions. Cerium is not toxic when consumed orally, but animals injected with large doses of cerium have died due to cardiovascular collapse. Cerium is more dangerous to aquatic organisms, on account of being damaging to cell membranes. Cerium(IV) oxide is a powerful oxidizing agent at high temperatures and will react with combustible organic materials. While cerium is not radioactive, the impure commercial grade may contain traces of thorium, which is weakly radioactive.
Biological Role:
Cerium can act similar to calcium in organisms, so accumulates in bones in small amounts. Cerium is also found in small amounts in tobacco plants, barley, and the wood of beech trees. However, very little cerium accumulates in the food chain. Human blood contains 0.001 ppm, human bones contain 3 ppm, and human tissue contains 0.3 ppm of cerium. There is a total of 40 milligrams of cerium in a typical 70-kilogram human. Humans typically consume less than a milligram per day of cerium. Cerium serves no known biological function, but cerium salts can stimulate metabolism.
Applications:
A major technological application for cerium(III) oxide is a catalytic converter for the reduction of CO emissions in the exhaust gases from motor vehicles. In particular, cerium oxide is added into diesel fuels. Another important use of the cerium oxide is a hydrocarbon catalyst in self cleaning ovens, incorporated into oven walls and as a petroleum cracking catalyst in petroleum refining.
Cerium(IV) oxide is considered one of the most efficient agents for precision polishing of optical components. Cerium compounds are also used in the manufacture of glass, both as a component and as a decolorizer. For example, cerium(IV) oxide in combination with titanium(IV) oxide gives a golden yellow color to glass; it also allows for selective absorption of ultraviolet light in glass. Cerium oxide has a high refractive index and is added to enamel to make it more opaque.
Cerium(IV) oxide is used in incandescent gas mantles, such as the Welsbach mantle, where it was combined with thorium, lanthanum, magnesium or yttrium oxides. Doped with other rare earth oxides, it has been investigated as a solid electrolyte in intermediate temperature solid oxide fuel cells: The cerium(IV) oxide-cerium(III) oxide cycle or CeO2/Ce2O3 cycle is a two step thermochemical process based on cerium(IV) oxide and cerium(III) oxide for hydrogen production.
The photostability of pigments can be enhanced by addition of cerium. It provides pigments with light fastness and prevents clear polymers from darkening in sunlight. Television glass plates are subject to electron bombardment, which tends to darken them by creation of F-center color centers. This effect is suppressed by addition of cerium oxide. Cerium is also an essential component of phosphors used in TV screens and fluorescent lamps. Cerium sulfide forms a red pigment that stays stable of to 350 °C. The pigment is a nontoxic alternative to cadmium sulfide pigments.
A traditional use of cerium was in the pyrophoric mischmetal alloy used for light flints. Because of the high affinity of cerium to sulfur and oxygen, it is used in various aluminium alloys, and iron alloys. In steels, cerium degasifies and can help reduce sulfides and oxides, and it is a precipitation hardening agent in stainless steel. Adding cerium to cast irons opposes graphitization and produces a malleable iron. Addition of 3–4% of cerium to magnesium alloys, along with 0.2 to 0.6% zirconium, helps refine the grain and give sound casting of complex shapes. It also adds heat resistance to magnesium castings. Cerium metal is sometimes added to aluminum to improve aluminum's corrosion resistance.
Cerium alloys are used in permanent magnets and in tungsten electrodes for gas tungsten arc welding. Cerium is used in carbon-arc lighting, especially in the motion picture industry. Cerium oxalate is an anti-emetic drug. Cerium(IV) sulfate is used extensively as a volumetric oxidizing agent in quantitative analysis. Ceric ammonium nitrate is a useful one-electron oxidant in organic chemistry, used to oxidatively etch electronic components, and as a primary standard for quantitative analysis.
Cerium is an iron-grey lustrous metal. It is malleable, and oxidises very readily at room temperature, especially in moist air. Except for europium, cerium is the most reactive of the rare-earth metals. It slowly decomposes in cold water, and rapidly in hot water. Alkali solutions and dilute and concentrated acids attack the metal rapidly. The pure metal may ignite when scratched with a knife. It reacts with all of the halides (F, Cl, Br, I)
It is the most abundant of the rare earth metals and is found in minerals including allanite, monazite, cerite, and bastnaesite. There are large deposits found in India, Brazil and the USA.
•Name: Cerium
•Symbol: Ce
•Atomic number: 58
•Atomic weight: 140.116 (1) [see note g]
•Standard state: solid at 298 K
•CAS Registry ID: 7440-45-1
•Group in periodic table:
•Group name: Lanthanoid
•Period in periodic table: 6 (lanthanoid)
•Block in periodic table: f-block
•Color: silvery white
•Classification: Metallic
Historical information
Cerium was discovered by Wilhelm von Hisinger, Jöns Jacob Berzelius, Martin Klaproth at 1803 in Sweden, and independently by Maratin Klparothe, Germany. Cerium was named by Berzelius after the dwarf planet Ceres, discovered two years earlier (1801) Ceres, which was itself named for the Roman goddess of agriculture. It was isolated from a mineral from an iron mine at Bastnas.
Physical properties
•Melting point: 1068 [or 795 °C (1463 °F)] K
•Boiling point: 3633 [or 3360 °C (6080 °F)] K
•Density of solid: 6689 kg m-3
Orbital properties
•Ground state electron configuration: [Xe].4f1.5d1.6s2
•Shell structure: 2.8.18.19.9.2
•Term symbol: 1G4
Isolation
Cerium metal is available commercially so it is not normally necessary to make it in the laboratory, which is just as well as it is difficult to isolate as the pure metal. This is largely because of the way it is found in nature. The lanthanoids are found in nature in a number of minerals. The most important are xenotime, monazite, and bastnaesite. The first two are orthophosphate minerals LnPO4 (Ln deonotes a mixture of all the lanthanoids except promethium which is vanishingly rare) and the third is a fluoride carbonate LnCO3F. Lanthanoids with even atomic numbers are more common. The most comon lanthanoids in these minerals are, in order, cerium, lanthanum, neodymium, and praseodymium. Monazite also contains thorium and ytrrium which makes handling difficult since thorium and its decomposition products are radioactive.
For many purposes it is not particularly necessary to separate the metals, but if separation into individual metals is required, the process is complex. Initially, the metals are extracted as salts from the ores by extraction with sulphuric acid (H2SO4), hydrochloric acid (HCl), and sodium hydroxide (NaOH). The ceric ion, Ce(IV) is more easily hydrolysed than the lanthanide (III) ions and therefore precipitates as a salt upon treatment with an oxidizing agent such as KMnO4.
Pure cerium is available through the electrolysis of a mixture of molten CeCl3 and NaCl (or CaCl2) in a graphite cell which acts as cathode using graphite as anode. The other product is chlorine gas.
Cerium, like all rare-earth metals, is of low to moderate toxicity. Cerium is a strong reducing agent and ignites spontaneously in air at 65 to 80 °C. Fumes from cerium fires are toxic. Water should not be used to stop cerium fires, as cerium reacts with water to produce hydrogen gas. Workers exposed to cerium have experienced itching, sensitivity to heat, and skin lesions. Cerium is not toxic when consumed orally, but animals injected with large doses of cerium have died due to cardiovascular collapse. Cerium is more dangerous to aquatic organisms, on account of being damaging to cell membranes. Cerium(IV) oxide is a powerful oxidizing agent at high temperatures and will react with combustible organic materials. While cerium is not radioactive, the impure commercial grade may contain traces of thorium, which is weakly radioactive.
Biological Role:
Cerium can act similar to calcium in organisms, so accumulates in bones in small amounts. Cerium is also found in small amounts in tobacco plants, barley, and the wood of beech trees. However, very little cerium accumulates in the food chain. Human blood contains 0.001 ppm, human bones contain 3 ppm, and human tissue contains 0.3 ppm of cerium. There is a total of 40 milligrams of cerium in a typical 70-kilogram human. Humans typically consume less than a milligram per day of cerium. Cerium serves no known biological function, but cerium salts can stimulate metabolism.
Applications:
A major technological application for cerium(III) oxide is a catalytic converter for the reduction of CO emissions in the exhaust gases from motor vehicles. In particular, cerium oxide is added into diesel fuels. Another important use of the cerium oxide is a hydrocarbon catalyst in self cleaning ovens, incorporated into oven walls and as a petroleum cracking catalyst in petroleum refining.
Cerium(IV) oxide is considered one of the most efficient agents for precision polishing of optical components. Cerium compounds are also used in the manufacture of glass, both as a component and as a decolorizer. For example, cerium(IV) oxide in combination with titanium(IV) oxide gives a golden yellow color to glass; it also allows for selective absorption of ultraviolet light in glass. Cerium oxide has a high refractive index and is added to enamel to make it more opaque.
Cerium(IV) oxide is used in incandescent gas mantles, such as the Welsbach mantle, where it was combined with thorium, lanthanum, magnesium or yttrium oxides. Doped with other rare earth oxides, it has been investigated as a solid electrolyte in intermediate temperature solid oxide fuel cells: The cerium(IV) oxide-cerium(III) oxide cycle or CeO2/Ce2O3 cycle is a two step thermochemical process based on cerium(IV) oxide and cerium(III) oxide for hydrogen production.
The photostability of pigments can be enhanced by addition of cerium. It provides pigments with light fastness and prevents clear polymers from darkening in sunlight. Television glass plates are subject to electron bombardment, which tends to darken them by creation of F-center color centers. This effect is suppressed by addition of cerium oxide. Cerium is also an essential component of phosphors used in TV screens and fluorescent lamps. Cerium sulfide forms a red pigment that stays stable of to 350 °C. The pigment is a nontoxic alternative to cadmium sulfide pigments.
A traditional use of cerium was in the pyrophoric mischmetal alloy used for light flints. Because of the high affinity of cerium to sulfur and oxygen, it is used in various aluminium alloys, and iron alloys. In steels, cerium degasifies and can help reduce sulfides and oxides, and it is a precipitation hardening agent in stainless steel. Adding cerium to cast irons opposes graphitization and produces a malleable iron. Addition of 3–4% of cerium to magnesium alloys, along with 0.2 to 0.6% zirconium, helps refine the grain and give sound casting of complex shapes. It also adds heat resistance to magnesium castings. Cerium metal is sometimes added to aluminum to improve aluminum's corrosion resistance.
Cerium alloys are used in permanent magnets and in tungsten electrodes for gas tungsten arc welding. Cerium is used in carbon-arc lighting, especially in the motion picture industry. Cerium oxalate is an anti-emetic drug. Cerium(IV) sulfate is used extensively as a volumetric oxidizing agent in quantitative analysis. Ceric ammonium nitrate is a useful one-electron oxidant in organic chemistry, used to oxidatively etch electronic components, and as a primary standard for quantitative analysis.
Monday, October 7, 2013
Lanthanum (57)
Lanthanum is silvery white, malleable, ductile, and soft
enough to be cut with a knife. It is one of the most reactive of the rare-earth
metals. It oxidises rapidly when exposed to air. Cold water attacks lanthanum
slowly, and hot water attacks it much more rapidly. The metal reacts directly
with elemental carbon, nitrogen, boron, selenium, silicon, phosphorus,
sulphur, and with halogens. It is a component of, misch metal (used for making
lighter flints).
•Name: Lanthanum
•Symbol: La
•Atomic number: 57
•Atomic weight: 138.90547 (7) [see note g]
•Standard state: solid at 298 K
•CAS Registry ID: 7439-91-0
•Group in periodic table:
•Group name: Lanthanoid
•Period in periodic table: 6 (lanthanoid)
•Block in periodic table: f-block
•Color: silvery white
•Classification: Metallic
Historical information
Lanthanum was discovered by Carl Gustaf Mosander at 1839 in Sweden, when he recognized the element lanthanum in impure cerium nitrate. Origin of name: from the Greek word "lanthanein" meaning "to lie hidden". His extraction resulted in the oxide lanthana (La2O3). A number of other lanthanides (rare-earths) were later discovered by identification of the impurities in yttrium and cerium compounds.
Physical properties
•Melting point: 1193 [or 920 °C (1688 °F)] K
•Boiling point: 3743 [or 3470 °C (6278 °F)] K
•Density of solid: 6146 kg m-3
Orbital properties
•Ground state electron configuration: [Xe].5d1.6s2
•Shell structure: 2.8.18.18.9.2
•Term symbol: 2D3/2
Isolation
Llanthanum metal is available commercially so it is not normally necessary to make it in the laboratory, which is just as well as it is difficult to separate it from as the pure metal. This is largely because of the way it is found in nature. The lanthanoids are found in nature in a number of minerals. The most important are xenotime, monazite, and bastnaesite. The first two are orthophosphate minerals LnPO4 (Ln deonotes a mixture of all the lanthanoids except promethium which is vanishingly rare) and the third is a fluoride carbonate LnCO3F. Lanthanoids with even atomic numbers are more common. The most comon lanthanoids in these minerals are, in order, cerium, lanthanum, neodymium, and praseodymium. Monazite also contains thorium and ytrrium which makes handling difficult since thorium and its decomposition products are radioactive.
For many purposes it is not particularly necessary to separate the metals, but if separation into individual metals is required, the process is complex. Initially, the metals are extracted as salts from the ores by extraction with sulphuric acid (H2SO4), hydrochloric acid (HCl), and sodium hydroxide (NaOH). Modern purification techniques for these lanthanoid salt mixtures are ingenious and involve selective complexation techniques, solvent extractions, and ion exchange chromatography.
Pure lanthanum is available through the reduction of LaF3 with calcium metal.
2LaF3 + 3Ca → 2La + 3CaF2
This would work for the other calcium halides as well but the product CaF2 is easier to handle under the reaction conditions (heat to 50°C above the melting point of the element in an argon atmosphere). Excess calcium is removed from the reaction mixture under vacuum.
•Name: Lanthanum
•Symbol: La
•Atomic number: 57
•Atomic weight: 138.90547 (7) [see note g]
•Standard state: solid at 298 K
•CAS Registry ID: 7439-91-0
•Group in periodic table:
•Group name: Lanthanoid
•Period in periodic table: 6 (lanthanoid)
•Block in periodic table: f-block
•Color: silvery white
•Classification: Metallic
Historical information
Lanthanum was discovered by Carl Gustaf Mosander at 1839 in Sweden, when he recognized the element lanthanum in impure cerium nitrate. Origin of name: from the Greek word "lanthanein" meaning "to lie hidden". His extraction resulted in the oxide lanthana (La2O3). A number of other lanthanides (rare-earths) were later discovered by identification of the impurities in yttrium and cerium compounds.
Physical properties
•Melting point: 1193 [or 920 °C (1688 °F)] K
•Boiling point: 3743 [or 3470 °C (6278 °F)] K
•Density of solid: 6146 kg m-3
Orbital properties
•Ground state electron configuration: [Xe].5d1.6s2
•Shell structure: 2.8.18.18.9.2
•Term symbol: 2D3/2
Isolation
Llanthanum metal is available commercially so it is not normally necessary to make it in the laboratory, which is just as well as it is difficult to separate it from as the pure metal. This is largely because of the way it is found in nature. The lanthanoids are found in nature in a number of minerals. The most important are xenotime, monazite, and bastnaesite. The first two are orthophosphate minerals LnPO4 (Ln deonotes a mixture of all the lanthanoids except promethium which is vanishingly rare) and the third is a fluoride carbonate LnCO3F. Lanthanoids with even atomic numbers are more common. The most comon lanthanoids in these minerals are, in order, cerium, lanthanum, neodymium, and praseodymium. Monazite also contains thorium and ytrrium which makes handling difficult since thorium and its decomposition products are radioactive.
For many purposes it is not particularly necessary to separate the metals, but if separation into individual metals is required, the process is complex. Initially, the metals are extracted as salts from the ores by extraction with sulphuric acid (H2SO4), hydrochloric acid (HCl), and sodium hydroxide (NaOH). Modern purification techniques for these lanthanoid salt mixtures are ingenious and involve selective complexation techniques, solvent extractions, and ion exchange chromatography.
Pure lanthanum is available through the reduction of LaF3 with calcium metal.
2LaF3 + 3Ca → 2La + 3CaF2
This would work for the other calcium halides as well but the product CaF2 is easier to handle under the reaction conditions (heat to 50°C above the melting point of the element in an argon atmosphere). Excess calcium is removed from the reaction mixture under vacuum.
Thursday, October 3, 2013
Barium (56)
Barium is a metallic element, soft, and when pure is silvery
white like lead. The metal oxidises very easily and it reacts with water or
alcohol. Barium is one of the alkaline-earth metals. Small amounts of barium
compounds are used in paints and glasses.
The result of adding different metal salts to a burning reaction mixture of potassium chlorate and sucrose. The red colour originates from strontium sulphate. The orange/yellow colour originates from sodium chloride. The green colour originates from barium chlorate and the blue colour originates from copper (I) chloride. The lilac colour that should be evident from the potassium chlorate is washed out by the other colours, all of which are more intense (only to be demonstrated by a professionally qualified chemist following a legally satisfactory hazard asessment). Improperly done, this reaction is dangerous!
•Name: Barium
•Symbol: Ba
•Atomic number: 56
•Atomic weight: 137.327 (7)
•Standard state: solid at 298 K
•CAS Registry ID: 7440-39-3
•Group in periodic table: 2
•Group name: Alkaline earth metal
•Period in periodic table: 6
•Block in periodic table: s-block
•Color: silvery white
•Classification: Metallic
Historical information
Barium was discovered by Sir Humphrey Davy at 1808 in England. Origin of name: from the Greek word "barys" meaning "heavy". Baryta (barium oxide, BaO) was distinguished from lime (calcium oxide, CaO) by Scheele in 1774. Elemental barium was isolated by Sir Humphrey Davy in 1808 who electrolysed molten baryta.
Sometime prior to the autumn of 1803, the Englishman John Dalton was able to explain the results of some of his studies by assuming that matter is composed of atoms and that all samples of any given compound consist of the same combination of these atoms. Dalton also noted that in series of compounds, the ratios of the masses of the second element that combine with a given weight of the first element can be reduced to small whole numbers (the law of multiple proportions). This was further evidence for atoms. Dalton's theory of atoms was published by Thomas Thomson in the 3rd edition of his System of Chemistry in 1807 and in a paper about strontium oxalates published in the Philosophical Transactions. Dalton published these ideas himself in the following year in the New System of Chemical Philosophy. The symbol used by Dalton for barium is a circle with has marks at 1,3,5,7,9, and 11 o'clock.
Physical properties
•Melting point: 1000 [or 727 °C (1341 °F)] K
•Boiling point: 2143 [or 1870 °C (3398 °F)] K
•Density of solid: 3510 kg m-3
Orbital properties
•Ground state electron configuration: [Xe].6s2
•Shell structure: 2.8.18.18.8.2
•Term symbol: 1S0
Isolation
Barium metal is available commercially and there is normally no need to make it in the laboratory. Commercially, it is made on small scale by the electrolysis of molten barium chloride, BaCl2.
cathode: Ba2+(l) + 2e- → Ba
anode: Cl-(l) → 1/2Cl2 (g) + e-
Barium metal can also be islated from the reduction of barium oxide, BaO, with aluminium.
The result of adding different metal salts to a burning reaction mixture of potassium chlorate and sucrose. The red colour originates from strontium sulphate. The orange/yellow colour originates from sodium chloride. The green colour originates from barium chlorate and the blue colour originates from copper (I) chloride. The lilac colour that should be evident from the potassium chlorate is washed out by the other colours, all of which are more intense (only to be demonstrated by a professionally qualified chemist following a legally satisfactory hazard asessment). Improperly done, this reaction is dangerous!
•Name: Barium
•Symbol: Ba
•Atomic number: 56
•Atomic weight: 137.327 (7)
•Standard state: solid at 298 K
•CAS Registry ID: 7440-39-3
•Group in periodic table: 2
•Group name: Alkaline earth metal
•Period in periodic table: 6
•Block in periodic table: s-block
•Color: silvery white
•Classification: Metallic
Historical information
Barium was discovered by Sir Humphrey Davy at 1808 in England. Origin of name: from the Greek word "barys" meaning "heavy". Baryta (barium oxide, BaO) was distinguished from lime (calcium oxide, CaO) by Scheele in 1774. Elemental barium was isolated by Sir Humphrey Davy in 1808 who electrolysed molten baryta.
Sometime prior to the autumn of 1803, the Englishman John Dalton was able to explain the results of some of his studies by assuming that matter is composed of atoms and that all samples of any given compound consist of the same combination of these atoms. Dalton also noted that in series of compounds, the ratios of the masses of the second element that combine with a given weight of the first element can be reduced to small whole numbers (the law of multiple proportions). This was further evidence for atoms. Dalton's theory of atoms was published by Thomas Thomson in the 3rd edition of his System of Chemistry in 1807 and in a paper about strontium oxalates published in the Philosophical Transactions. Dalton published these ideas himself in the following year in the New System of Chemical Philosophy. The symbol used by Dalton for barium is a circle with has marks at 1,3,5,7,9, and 11 o'clock.
Physical properties
•Melting point: 1000 [or 727 °C (1341 °F)] K
•Boiling point: 2143 [or 1870 °C (3398 °F)] K
•Density of solid: 3510 kg m-3
Orbital properties
•Ground state electron configuration: [Xe].6s2
•Shell structure: 2.8.18.18.8.2
•Term symbol: 1S0
Isolation
Barium metal is available commercially and there is normally no need to make it in the laboratory. Commercially, it is made on small scale by the electrolysis of molten barium chloride, BaCl2.
cathode: Ba2+(l) + 2e- → Ba
anode: Cl-(l) → 1/2Cl2 (g) + e-
Barium metal can also be islated from the reduction of barium oxide, BaO, with aluminium.