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Cerium

What is Cerium

Cerium (pronunciation: SER-ee-em) is a soft, grayish metal that belongs to the group of lanthanides and is represented by the chemical symbol Ce [1, 2]. Its naturally-occurring isotopes include Cerium-136, Cerium-138, Cerium-140, and Cerium-142, out of which Cerium-140 is the most abundant (with 88.48% natural abundance) [3]. Among the 35 known radioisotopes of cerium, the most stable is Cerium-144 that is characterized by a half-life period of 284.893 days [3].

Cerium

Where is Cerium Found

Cerium is commonly found in rare earth minerals like bastnaesite and monazite [1]. The mineral ore is heated and then treated with hydrochloric acid to produce cerium oxide from which metallic cerium is isolated through electrochemical reduction [1]. The metal can also be obtained through thermal reduction of cerium fluoride with calcium [1, 4]. While China, the CIS countries, and the USA have the highest cerium reserves, the top 3 cerium producing countries in the world are China, Russia, and Malaysia [1].

Cerium Element 58

History

Origin of its Name: It is named after ‘Ceres’, an asteroid that was named after the Roman goddess of fertility and agriculture [1].

Who discovered it: The element was discovered by the Swedish chemists, Jöns Jacob Berzelius along with Wilhelm von Hisinger, and independently by the German chemist Martin Klaproth [1, 4].

When and How was it Discovered

In 1803, Berzelius and Hisinger discovered the new element from a reddish-brown cerium salt called cerite [1, 5]. While investigating the chemical reaction of the cerium salts, they found the two oxidation states – one of which producing yellowish-red salts and the other colorless ones [5]. Although they did not isolate the pure form, they named the element ‘cerium’ and its oxide ‘ceria’ [5].

Martin Klaproth analyzed the salt and concluded that it consists of an oxide of a new metallic element [5]. He named the oxide ‘ockroite’ because of its yellowish-red color [5]. However, the result of Berzelius and Hisinger was published before that of Klaproth, and so the name cerium was approved [5].

Cerium Oxide Powder

Cerium Identification

Atomic number 58 [1]
CAS number 7440-45-1 [1]
Position in the periodic table Group Period Block
  Lanthanides [1] 6 [1] f [1]

Properties and Characteristics of Cerium

General Properties

Atomic mass 140.116 amu [1]
Relative atomic mass 140.116 [1]

Physical Properties

Color Gray [1, 5]
Melting point/freezing point 799 °C, 1470 °F [1]
Boiling point 3443 °C, 6229 °F [1]
Density 6.77 g cm-3 [1]
State of matter at room temperature (solid/liquid/gas) Solid [1, 5]
Hardness
– Brinell 412 MPa [6]
– Mohs 2.5 [6]
– Vickers 270 MPa [6]
Electrical conductivity 1.4X106 S/m [6]
Thermal (heat) conductivity 11 W/(m K) [6]
Specific heat 192 J kg-1 K-1 [1]
Bulk modulus 21.5 GPa [1]
Shear modulus 13.5 GPa [1]
Young’s modulus 33.6 GPa [1]
Vapor pressure
– Temperature (K) 400 600 800 1000 1200 1400 1600 1800 2000 2200 2400
– Pressure (Pa) 2.47 X 10-11 8.91 X 10-8 2.97 X 10-5 2.33 X 10-3 6.91 X 10-2 1.04 9.56 60.8

Chemical Properties

Oxidation states 4, 3 [1]
Isotopes Isotope Mass Abundance (%) Half-life Mode of decay
  136Ce 135.907 0.185 >0.7 X 1014 y EC EC
  >4.2 X 1015 y β-β-
  138Ce 137.906 0.251 >3.7 X 1014 y EC EC
  140Ce 139.905 88.45
  142Ce 141.909 11.114 >1.6 X 1017 y β-β-

Atomic Data of Cerium (Element 58)

Valence electrons 2 [7]
Quantum numbers
– n 4 [7]
– ℓ 3 [7]
– m -2 [7]
– ms +1/2 [7]
Electron configuration (noble gas configuration) [Xe] 4f15d16s2 [1]
Atomic structure
– Number of electrons 58 [5]
– Number of neutrons 82 [5]
– Number of protons 58 [5]
Radius of Atom
– Atomic radius 2.42 Å [1]
– Covalent radius 1.84 Å [1]
Electronegativity (Pauling-scale) 1.12 [1]
Electron affinity 62.72 kJ mol-1 [1]
Ionization energy (kJ mol-1) 1st 2nd 3rd 4th 5th 6th 7th 8th
  534.403 1046.87 2697.73 3546.608 6324.61 7487.3

Cerium Electron Configuration (Bohr Model)

What is It Used for

  • The mischmetal alloy made of cerium, lanthanum, neodymium, and praseodymium mixed with magnesium oxide and iron oxide is used as flints for lighting cigarettes and gas [1, 5].
  • Cerium oxide, as a catalyst, is used in self-cleaning ovens for preventing the accumulation of cooking residues and for polishing glass surfaces [1, 5].
  • It is used in catalytic converters because it helps reduce automobile exhaust emissions [1]. Cerium oxide nanoparticles are added to diesel for reducing the emission of soot and improving engine performance of vehicles [5].
  • Cerium sulfide is non-toxic by nature and is used as a coloring pigment because of its rich red color [1].
  • The element is used in phosphors in flat-screen televisions, floodlights, and energy-efficient light bulbs [1].
  • Flammacerium, a compound containing cerium nitrate and silver sulfadiazine, is a topical ointment used for treating infections in burn wounds [5].

Cerium Toxicity

The element 58 has no known biological roles and is low to moderate in toxicity [1, 5].

Cerium Symbol

Interesting Facts

  • The image of cerium is a graphical representation of the asteroid Ceres, whereas the background is derived from an astronomical map of the 17th-century [1].
  • Its natural abundance is almost similar to zinc, but it is more than lead or tin [1].
  • At room temperature, the element can readily oxidize [4].
  • Pure cerium may ignite if scratched with a sharp metal object such as a knife [4].
  • It decomposes in water to produce cerium hydroxide and hydrogen [5].

Cost of Cerium

The cost of 100 grams of pure cerium is about $380, but in bulk, it is about $1.20 [5].

References

  1. http://www.rsc.org/periodic-table/element/58/cerium
  2. https://education.jlab.org/itselemental/ele058.html
  3. https://www.webelements.com/cerium/isotopes.html
  4. https://www.livescience.com/37606-cerium.html
  5. https://www.chemicool.com/elements/cerium.html
  6. http://periodictable.com/Elements/058/data.html
  7. http://chemistry-reference.com/q_elements.asp?Symbol=Ce&language=en

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