Cerium(Ce) Element: Properties, Reaction, Uses, Effects

Cerium is a chemical element with the atomic number 58 and is represented by the symbol ‘Ce’ in the periodic table. It is soft and silvery-white in appearance and classified as rare earth metal and belongs to the f-block of the lanthanide group of the periodic table. Similar to the majority of other rare earth elements, the customary oxidation state of this particular element is +3. However, it is worth noting that certain compounds have been identified wherein the oxidation state is +2.

Cerium is the twenty-fifth-most prevalent element making up 66 ppm (parts per million) of the Earth’s crust. In the Earth’s crust, it is almost five times as prevalent as lead. Ce is not rare, as it is found in a variety of minerals, although the minerals belonging to the monazite and bastnäsite groups are considered the most significant sources in commercial applications. In these groups, cerium comprises approximately 50% of the total lanthanide content.

History of Cerium

• The element cerium was first identified in the year 1803 by Jacob Berzelius and Wilhelm von Hisinger in Sweden. Coincidentally, Martin Klaproth in Germany also independently discovered cerium during the same year.
•  Their finding was made through the examination of a cerium salt known as cerite, which possessed a reddish-brown hue. During the examination of the chemical reaction involving cerium salts, researchers observed the presence of two distinct oxidation states. One of these states resulted in the formation of yellowish-red salts, while the other state led to the production of colorless salts. Despite their inability to successfully isolate the pure form, the researchers assigned the name ‘cerium’ to the element and ‘ceria’ to its oxide.
• Martin Klaproth conducted an analysis of the salt and arrived at the conclusion that it comprises an oxide of a previously unidentified metallic element. The oxide was designated as ‘ockroite’ due to its characteristic yellowish-red hue. Nevertheless, the findings of Berzelius and Hisinger were documented and made public prior to Klaproth’s discovery, leading to the acceptance of the name cerium.
• It is named after Ceres, an asteroid named for the Roman deity of fertility and agriculture.

Occurrence of Cerium

• Ce exhibits the highest abundance among the lanthanide elements. The element does not occur naturally in a free state but rather is present in several minerals, primarily allanite, bastnasite, and monazite.
• Ce is commonly produced through the method of electrolysis of its chloride compound or through the reduction of the fused fluoride compound using calcium.
• Ce stands out among the lanthanide elements as the most readily extractable from its minerals due to its unique ability to attain a stable +4 oxidation state in an aqueous solution. Due to the diminished solubility of Ce in its +4 oxidation state, there is a tendency for cerium to exhibit depletion in rocks compared to other rare-earth elements. This phenomenon occurs as cerium becomes incorporated into zircon, facilitated by the similarity in charge and ionic radii between Ce⁴⁺ and Zr⁴⁺.

Isotopes of Cerium

Cerium exhibits a total of 30 isotopes, encompassing mass numbers ranging from 123 to 152, for which the respective half-lives have been determined. Ce found in nature is comprised of a combination of four isotopes.

There are four naturally occurring stable isotopes of cerium: ¹³⁶Ce, ¹³⁸Ce, ¹⁴⁰Ce, and ¹⁴²Ce.

Naturally Occurring Isotopes of Cerium

Elemental Properties of Cerium

Physical Properties of Cerium

• Cerium has an atomic number of 58 and is a silvery-white rare earth metal. It has a melting point of 795 °C ​(1463 °F) and a boiling point of 3443 °C (​6229 °F).
• Ce has a solid phase density of 6.770 g/cm³ and a liquid or molten phase density of 6.55 g/cm³.
• It has a hardness similar to that of silver.
• Ce is malleable which means it can be easily beaten into thin sheets without any cleavage.
• Ce is ductile which means it is possible to draw thin wires from it without breaking.
• Cerium exhibits four distinct allotropic forms, including two face-centered cubic structures, one body-centered cubic structure, as well as a hexagonal close-packed arrangement.

Chemical properties of Cerium

• Ce undergoes oxidation upon exposure to atmospheric oxygen, resulting in the formation of a tarnished surface. The object undergoes corrosion when exposed to atmospheric conditions. The existence of a spalling oxide layer can be regarded as an indication of the ongoing corrosion process.
• The reaction between cerium metal and water results in the formation of cerium (III) hydroxide. The rate of a chemical reaction is observed to exhibit a positive correlation with the temperature of the aqueous medium.
• The ground metal of cerium is highly pyrophoric, which means that it rapidly catches fire with even the smallest amount of stimulus.
• Ce exhibits a high propensity for combustion at a temperature of 150°C, resulting in the formation of ceria, a compound commonly referred to as cerium (IV) oxide.
• The sole halogenated compounds identified for Ce are cerium tetrafluoride and cerium diiodide.

Chemical Reaction of Cerium

• The Reaction of Cerium With Air

Ce metal undergoes gradual oxidation in the presence of atmospheric oxygen, resulting in the formation of Ce (IV) oxide, denoted as CeO₂, which exhibits a propensity for combustion.

Ce (s) + O₂ (g) → CeO₂ (s)

• The Reaction of Cerium With Water

Ce, a metallic element that has a silvery-white appearance, exhibits notable electropositive properties. It undergoes a gradual reaction with cold water and a more rapid reaction with hot water, resulting in the formation of cerium hydroxide (Ce[OH]₃) and the liberation of hydrogen gas (H₂).

2 Ce (s) + 6 H₂O (g) → 2 Ce(OH)₃ (aq) + 3 H₂ (g)

• The Reaction of Cerium With Halogens

Ce metal exhibits reactivity with various halogens, resulting in the formation of cerium (III) halides.

The chemical reaction between cerium metal and fluorine gas (F₂) results in the formation of cerium (III) fluoride (CeF₃).

2 Ce (s) + 3 F₂ (g) → 2CeF₃ (s) [white]

The chemical reaction between Ce metal and chlorine, represented by Cl₂, results in the formation of cerium (III) chloride, denoted as CeCl₃.

2 Ce (s) + 3 Cl₂ (g) → 2 CeCl₃ (s) [white]

The chemical reaction between Ce metal and bromine, represented by Br₂, results in the formation of cerium (III) bromide, denoted as CeBr₃.

2 Ce (s) + 3 Br₂ (g) → 2 CeBr₃ (s) [white]

The chemical reaction between Ce metal and iodine (I₂) results in the formation of Ce(III) iodide, denoted as CeI₃.

2 Ce (s) + 3 I₂ (g) → 2 CeI₃ (s) [yellow]

• The Reaction of Cerium With Acid

The dissolution of Ce metal in a diluted form of sulphuric acid leads to the formation of solutions that contain the colorless aquated Ce (III) ion, along with the liberation of hydrogen gas, H₂. There is a high probability that Ce³⁺(aq) predominantly exists in the form of the complex ion [Ce(OH₂)₉]³⁺.

2 Ce (s) + 3 H₂SO₄(aq) → 2Ce³⁺ (aq) + 3 SO₄^2- (aq) + 3 H₂ (g)

Uses of Cerium

Ce is used in various industries some of which are discussed below:

Used In Glass And Ceramics

Ce metal and its associated compounds possess a diverse range of applications, particularly within the domains of glass and ceramics. Ce and its compounds are incorporated into these materials for the purpose of introducing a yellow hue, eliminating undesired pigmentation, rendering glass responsive to specific forms of radiation, imparting distinctive optical properties to glass, and enhancing the structural integrity of select dental materials.

Used In Alloys

Ce is utilized in conjunction with aluminum in the production of castable eutectic aluminum alloys, which exhibit exceptional strength at elevated temperatures. Plutonium-cerium alloys have been employed as nuclear fuels in various applications. An alloy comprising Ce and La, alongside minute quantities of neodymium and praseodymium (commonly referred to as misch metal), is combined with iron oxide and magnesium oxide. This alloy serves as the flint component in gas lighters.

Used In Electronics Industry

The incorporation of Ce oxide into the glass plates of cathode-ray tube televisions served as a preventive measure against the phenomenon of darkening that occurred as a consequence of electron bombardment during the operational process. Ce is a crucial dopant in the production of phosphors utilized in cathode ray tube (CRT) television screens, white light-emitting diodes (LEDs), and fluorescent lamps.

Miscellaneous Uses of Cerium

• Ce lasers have important new uses. Lasers emit bright, single-color light. Ce lasers use lithium, strontium, aluminum, and fluorine crystals with a little quantity of Ce. Ce lasers emit ultraviolet light. Ultraviolet radiation resembles blue and violet light but is invisible. Cerium lasers detect air pollutants ozone and sulfur dioxide.
• Ce oxide serves as a catalyst in automotive catalytic converters, facilitating the reduction of carbon monoxide emissions present in the exhaust gases of automobiles.
• The addition of Ce oxide nanopowder to diesel fuel has been found to effectively mitigate the emission of soot particles and enhance the overall performance of engines. This material finds application in the construction of self-cleaning oven walls, as well as in the polishing of glass surfaces.
• Ce oxide, in the form of cerium, finds another practical application in internal combustion engines, such as those commonly found in automobiles. The incorporation of cerium oxide (CeO₂) into the fuel of an engine facilitates a more efficient combustion process, resulting in reduced emission of pollutants.
• Ce oxide is additionally employed as an abrasive agent. An abrasive refers to a particulate substance employed for the purpose of grinding or polishing various materials. Ce oxide has been adopted as a replacement for the previously utilized abrasive substance, commonly referred to as rouge, in the process of polishing specialized glass surfaces, including telescope mirrors.

Health Effects of Cerium

• Ce is classified as a rare chemical element that is commonly present in residential settings, specifically within various household appliances including color televisions, fluorescent lamps, energy-saving lamps, and glass materials. All rare chemicals exhibit similar properties.
• Ce poses a significant occupational hazard primarily attributable to the inhalation of vapors and gases in the workplace setting. Prolonged exposure to this substance has the potential to induce pulmonary embolisms, particularly in the context of extended periods of exposure. The accumulation of Ce within the human body has the potential to pose a risk to the liver.
• Ce is currently not attributed with any established biological function; however, it has been observed that Ce salts possess the ability to enhance metabolic activity.

Environmental Effects of Cerium

• Ce, an element of the lanthanide series, is ubiquitously dispersed within the environment, primarily as a consequence of its release by industries involved in the production of petroleum-based products.
• Ce, over time, exhibits a propensity for gradual accumulation within terrestrial and aquatic environments, thereby engendering a subsequent rise in concentrations within the realms of human and animal populations, as well as soil particulate matter.
• The presence of Ce in aquatic organisms elicits detrimental effects on cellular membranes, thereby engendering deleterious consequences on reproductive processes and the intricate workings of the nervous system.
• Catalytic converters employ cerium to improve city air quality. Diesel engines release carbon particulates. Burning particulates in a ceramic filter reduces emissions. When added to fuel, Ce oxide catalyzes particle combustion and eliminates them.

Video on Cerium Element

References

• Emsley, John (2011). Nature’s Building Blocks: An A–Z Guide to the Elements (2nd ed.). Oxford: Oxford University Press. ISBN 978-0-19-960563-7.
• Greenwood, N. N.; Earnshaw, A. (1998). Chemistry of the Elements (2nd ed.). Oxford: Butterworth Heinemann. ISBN 0-7506-3365-4.
• Haynes, William M., ed. (2011). CRC Handbook of Chemistry and Physics (92nd ed.). Boca Raton, FL: CRC Press. p. 4.121. ISBN 1-4398-5511-0.
• https://byjus.com/chemistry/cerium/
• https://www.chemicool.com/elements/cerium.html
• https://www.lenntech.com/periodic/elements/ce