Science / Periodic Table of Elements / Cerium (Ce): Atomic number: 58, Atomic mass: 140.12 g.mol -1, Electronegativity: 1.1, Density: 6.76 g.cm-3 at 20Â°C, Melting point: 799 Â°C, Boiling point: 3426 Â°C, Vanderwaals radius: 0.181 nm, Ionic radius: 0.102 nm (+3) ; 0,087 nm (+4), Isotopes: 9, Electronic shell: [ Xe ] 4f1 5d1 6s2, Energy of first ionisation: 526.8 kJ.mol -1, Energy of second ionisation: 1045 kJ.mol -1, Energy of third ionisation: 1945.6 kJ.mol -1, Energy of fourth ionisation: 3537 kJ.mol -1, Standard Potential: - 2.48 V ( Ce3+/ Ce ), Discovered by: W. von Hisinger in 1903. Cerium is a malleable, soft, ductile, iron-grey metal, slightly harder than lead. It is very reactive: it tarnishes readily in the air, it oxidizes slowly in cold water and rapidly in hot water. It dissolves in acids. It can burn when heated or scratched with a knife. Applications: The metal is used as a core for the carbon electrodes of arc lamps, for incandescent mantles for gas lighting. Cerium is used in aluminium and iron alloys, in stainless steel as a precipitation hardening agent, to make permanent magnets. Cerium oxide is part of the catalyst of catalytic converters used to clean up exhaust vehicles, it also catalyzes the reduction of nitrogen oxides (NOx) to nitrogen gas. All new cars are now equipped with catalytic conveter which consist in a ceramic or metal substrate, a coating of aluminium and cerium oxides and a layer of finely dispersed metal such as platinum or rhodium, which is the active surface. Cerium sulphide (Ce2S3) is likely to replace cadmium in red pigments for containers, toys, household wares and crates, since cadmium is now considered environmentally undesiderable. Other uses of cerium are in flat-screen televisions, low-energy light bulbs and magnetic-optic compact discs, in chromium plating. The use of cerium is still growing, due to the fact that it is suited to produce catalysers and to polish glass. Cerium in the environment: Cerium is the most abundant of the rare earth elements. It makes up about 0.0046 % of the Earth's crust by weight. Cerium comes mainly from the major lanthanide ores but some is obtained from perovskite, a titanium mineral and allanite, both of which can have enough cerium to make them viable sources. Production amounts to 23.000 tonnes a year, but this amount is likely to increase since more and more cerium is used nowadays.
Science / Periodic Table of Elements / Cerium (Ce): Atomic number: 58, Atomic mass: 140.12 g.mol -1, Electronegativity: 1.1, Density: 6.76 g.cm-3 at 20Â°C, Melting point: 799 Â°C, Boiling point: 3426 Â°C, Vanderwaals radius: 0.181 nm, Ionic radius: 0.1 MORE