CERIUM

Introduction

Atomic Number: 58
Group: None
Atomic Weight: 140.116
Period: 6
CAS Number: 7440-45-1

Classification

Chalcogen
Halogen
Noble Gas
Lanthanoid
Actinoid
Rare Earth Element
Platinum Group Metal
Transuranium
No Stable Isotopes
Solid
Liquid
Gas
Solid (Predicted)

Description • Uses/Function

Discovered in 1803 by Klaproth and by Berzelius and Hisinger; metal prepared by Hillebrandand Norton in 1875. Cerium is the most abundant of the metals of the so-called rare earths. It is found in a number of minerals including allanite (alsoknown as orthite), monazite, bastnasite, cerite, and samarskite. Monazite and bastnasite are presently the two most important sources of cerium. Largedeposits of monazite found on the beaches of Travancore, India, in river sands in Brazil, and deposits of allanite in the western United States, andbastnasite in Southern California will supply cerium, thorium, and the other rare-earth metals for many years to come. Metallic cerium is preparedby metallothermic reduction techniques, such as by reducing cerous fluoride with calcium, or by electrolysis of molten cerous chloride or other ceroushalides. The metallothermic technique is used to produce high-purity cerium. Cerium is especially interesting because of its variable electronicstructure. The energy of the inner 4f level is nearly the same as that of the outer or valence electrons, and only small amounts of energy are requiredto change the relative occupancy of these electronic levels. This gives rise to dual valency states. For example, a volume change of about 10% occurswhen cerium is subjected to high pressures or low temperatures. It appears that the valence changes from about 3 to 4 when it is cooled or compressed.The low temperature behavior of cerium is complex. Four allotropic modifications are thought to exist: cerium at room temperature and at atmosphericpressure is known as g cerium. Upon cooling to –16°C, g cerium changes to b cerium. The remaining g cerium starts to change to a cerium when cooledto –172°C, and the transformation is complete at –269°C. a Cerium has a density of 8.16; d cerium exists above 726°C. At atmospheric pressure, liquidcerium is more dense than its solid form at the melting point. Cerium is an iron-gray lustrous metal. It is malleable, and oxidizes very readily at roomtemperature, 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 is likely to ignite if scratched witha knife. Ceric salts are orange red or yellowish; cerous salts are usually white. Cerium is a component of misch metal, which is extensively used inthe manufacture of pyrophoric alloys for cigarette lighters, etc. Natural cerium is stable and contains four isotopes. Thirty five other radioactive isotopesand isomers are known. While cerium is not radioactive, the impure commercial grade may contain traces of thorium, which is radioactive. The oxideis an important constituent of incandescent gas mantles and it is emerging as a hydrocarbon catalyst in “self-cleaning” ovens. In this application it canbe incorporated into oven walls to prevent the collection of cooking residues. As ceric sulfate it finds extensive use as a volumetric oxidizing agentin quantitative analysis. Cerium compounds are used in the manufacture of glass, both as a component and as a decolorizer. The oxide is findingincreased use as a glass polishing agent instead of rouge, for it is much faster than rouge in polishing glass surfaces. Cerium, with other rare earths,is used in carbon-arc lighting, especially in the motion picture industry. It is also finding use as an important catalyst in petroleum refining and inmetallurgical and nuclear applications. In small lots, 99.9% cerium costs about $4/g (99.9%). 1

• "in wine-bottle glass promotes absorption of UV light." 2
• "catalyst in refining oil to gasoline" 3

Physical Properties

Melting Point:4*  798 °C = 1071.15 K = 1468.4 °F
Boiling Point:4* 3443 °C = 3716.15 K = 6229.4 °F
Sublimation Point:4 
Triple Point:4 
Critical Point:4 
Density:5  6.770 g/cm3

* - at 1 atm

Electron Configuration

Electron Configuration:  *[Xe] 6s2 4f2
Block: f
Highest Occupied Energy Level: 6
Valence Electrons: 2

Quantum Numbers:

n = 4
ℓ = 3
m = -2
ms = +½

Bonding

Electronegativity (Pauling scale):6 1.12
Electropositivity (Pauling scale): 2.88
Work Function:7 2.80 eV = 4.4856E-19 J

Ionization Potential   eV 8  kJ/mol  
1 5.5387    534.4
2 10.85    1046.9
Ionization Potential   eV 8  kJ/mol  
3 20.198    1948.8
4 36.758    3546.6
Ionization Potential   eV 8  kJ/mol  
5 65.55    6324.6
6 77.6    7487.3

Thermochemistry

Specific Heat: 0.192 J/g°C 9 = 26.902 J/mol°C = 0.046 cal/g°C = 6.430 cal/mol°C
Thermal Conductivity: 11.4 (W/m)/K, 27°C 10
Heat of Fusion: 5.46 kJ/mol 11 = 39.0 J/g
Heat of Vaporization: 414 kJ/mol 12 = 2954.7 J/g
State of Matter Enthalpy of Formation (ΔHf°)13 Entropy (S°)13 Gibbs Free Energy (ΔGf°)13
(kcal/mol) (kJ/mol) (cal/K) (J/K) (kcal/mol) (kJ/mol)
(s) 0 0 17.2 71.9648 0 0
(g) 101 422.584 45.81 191.66904 92 384.928

Isotopes

Nuclide Mass 14 Half-Life 14 Nuclear Spin 14 Binding Energy
119Ce 118.95276(64)# 200# ms 5/2+# 961.68 MeV
120Ce 119.94664(75)# 250# ms 0+ 979.07 MeV
121Ce 120.94342(54)# 1.1(1) s (5/2)(+#) 987.14 MeV
122Ce 121.93791(43)# 2# s 0+ 1,004.53 MeV
123Ce 122.93540(32)# 3.8(2) s (5/2)(+#) 1,012.60 MeV
124Ce 123.93041(32)# 9.1(12) s 0+ 1,020.67 MeV
125Ce 124.92844(21)# 9.3(3) s (7/2-) 1,038.06 MeV
126Ce 125.92397(3) 51.0(3) s 0+ 1,046.13 MeV
127Ce 126.92273(6) 29(2) s 5/2+# 1,054.20 MeV
128Ce 127.91891(3) 3.93(2) min 0+ 1,071.59 MeV
129Ce 128.91810(3) 3.5(3) min (5/2+) 1,079.66 MeV
130Ce 129.91474(3) 22.9(5) min 0+ 1,087.73 MeV
131Ce 130.91442(4) 10.2(3) min (7/2+) 1,095.80 MeV
132Ce 131.911460(22) 3.51(11) h 0+ 1,103.87 MeV
133Ce 132.911515(18) 97(4) min 1/2+ 1,111.94 MeV
134Ce 133.908925(22) 3.16(4) d 0+ 1,129.33 MeV
135Ce 134.909151(12) 17.7(3) h 1/2(+) 1,137.40 MeV
136Ce 135.907172(14) STABLE 0+ 1,145.47 MeV
137Ce 136.907806(14) 9.0(3) h 3/2+ 1,153.54 MeV
138Ce 137.905991(11) STABLE 0+ 1,161.61 MeV
139Ce 138.906653(8) 137.641(20) d 3/2+ 1,169.68 MeV
140Ce 139.9054387(26) STABLE 0+ 1,177.76 MeV
141Ce 140.9082763(26) 32.508(13) d 7/2- 1,185.83 MeV
142Ce 141.909244(3) STABLE 0+ 1,193.90 MeV
143Ce 142.912386(3) 33.039(6) h 3/2- 1,192.66 MeV
144Ce 143.913647(4) 284.91(5) d 0+ 1,200.73 MeV
145Ce 144.91723(4) 3.01(6) min (3/2-) 1,208.80 MeV
146Ce 145.91876(7) 13.52(13) min 0+ 1,216.87 MeV
147Ce 146.92267(3) 56.4(10) s (5/2-) 1,215.63 MeV
148Ce 147.92443(3) 56(1) s 0+ 1,223.70 MeV
149Ce 148.9284(1) 5.3(2) s (3/2-)# 1,231.77 MeV
150Ce 149.93041(5) 4.0(6) s 0+ 1,230.52 MeV
151Ce 150.93398(11) 1.02(6) s 3/2-# 1,238.60 MeV
152Ce 151.93654(21)# 1.4(2) s 0+ 1,246.67 MeV
153Ce 152.94058(43)# 500# ms [>300 ns] 3/2-# 1,245.42 MeV
154Ce 153.94342(54)# 300# ms [>300 ns] 0+ 1,253.49 MeV
155Ce 154.94804(64)# 200# ms [>300 ns] 5/2-# 1,261.57 MeV
156Ce 155.95126(64)# 150# ms 0+ 1,260.32 MeV
157Ce 156.95634(75)# 50# ms 7/2+# 1,268.39 MeV
Values marked # are not purely derived from experimental data, but at least partly from systematic trends. Spins with weak assignment arguments are enclosed in parentheses. 14

Abundance

Earth - Source Compounds: phosphates 15
Earth - Seawater: 0.0000012 mg/L 16
Earth -  Crust:  66.5 mg/kg = 0.00665% 16
Earth -  Total:  1010 ppb 17
Mercury -  Total:  780 ppb 17
Venus -  Total:  1060 ppb 17
Chondrites - Total: 1.2 (relative to 106 atoms of Si) 18

Compounds

Safety Information


Material Safety Data Sheet - ACI Alloys, Inc.

For More Information

External Links:

Magazines:
(1) Folger, Tim. The Secret Ingredients of Everything. National Geographic, June 2011, pp 136-145.

Sources

(1) - Lide, David R. CRC Handbook of Chemistry and Physics, 83rd ed.; CRC Press: Boca Raton, FL, 2002; p 4:8.
(2) - Folger, Tim. The Secret Ingredients of Everything. National Geographic, June 2011, p 140.
(3) - Folger, Tim. The Secret Ingredients of Everything. National Geographic, June 2011, p 143.
(4) - Lide, David R. CRC Handbook of Chemistry and Physics, 83rd ed.; CRC Press: Boca Raton, FL, 2002; p 4:132.
(5) - Lide, David R. CRC Handbook of Chemistry and Physics, 84th ed.; CRC Press: Boca Raton, FL, 2002; p 4:39-4:96.
(6) - Dean, John A. Lange's Handbook of Chemistry, 11th ed.; McGraw-Hill Book Company: New York, NY, 1973; p 4:8-4:149.
(7) - Speight, James. Lange's Handbook of Chemistry, 16th ed.; McGraw-Hill Professional: Boston, MA, 2004; p 1:132.
(8) - Lide, David R. CRC Handbook of Chemistry and Physics, 83rd ed.; CRC Press: Boca Raton, FL, 2002; p 10:178 - 10:180.
(9) - Lide, David R. CRC Handbook of Chemistry and Physics, 83rd ed.; CRC Press: Boca Raton, FL, 2002; p 4:133.
(10) - Lide, David R. CRC Handbook of Chemistry and Physics, 83rd ed.; CRC Press: Boca Raton, FL, 2002; pp 6:193, 12:219-220.
(11) - Lide, David R. CRC Handbook of Chemistry and Physics, 83rd ed.; CRC Press: Boca Raton, FL, 2002; pp 6:123-6:137.
(12) - Lide, David R. CRC Handbook of Chemistry and Physics, 83rd ed.; CRC Press: Boca Raton, FL, 2002; pp 6:107-6:122.
(13) - Dean, John A. Lange's Handbook of Chemistry, 12th ed.; McGraw-Hill Book Company: New York, NY, 1979; p 9:4-9:94.
(14) - Atomic Mass Data Center. http://amdc.in2p3.fr/web/nubase_en.html (accessed July 14, 2009).
(15) - Silberberg, Martin S. Chemistry: The Molecular Nature of Matter and Change, 4th ed.; McGraw-Hill Higher Education: Boston, MA, 2006, p 965.
(16) - Lide, David R. CRC Handbook of Chemistry and Physics, 83rd ed.; CRC Press: Boca Raton, FL, 2002; p 14:17.
(17) - Morgan, John W. and Anders, Edward, Proc. Natl. Acad. Sci. USA 77, 6973-6977 (1980)
(18) - Brownlow, Arthur. Geochemistry; Prentice-Hall, Inc.: Englewood Cliffs, NJ, 1979, pp 15-16.