Catégories
> CHIMIE, SUBSTANCES, PROCESSUS > élément chimique > élément de transition One of a group of metallic elements in which the members have the filling of the outermost shell to 8 electrons interrupted to bring the penultimate shell from 8 to 18 or 32 electrons; includes elements 21 through 29 (scandium through copper), 39 through 47 (yttrium through silver), 57 through 79 (lanthanum through gold), and all known elements from 89 (actinium) on.
 A radioactive element of the actinide series, occurring as a decay product of uranium. It is used as an alpha particle source and in neutron production. actinium |
 A very ductile malleable brilliant greyish-white element having the highest electrical and thermal conductivity of any metal. It occurs free and in argentite and other ores: used in jewellery, tableware, coinage, electrical contacts, and in electroplating. Its compounds are used in photography. argent |
| One of the toxic heavy metal which has caused deaths and permanent illnesses in a series of major pollution incidents around the world. Cadmium has no useful biological purpose. However, it has wide industrial applications. It has been used for decades in metal plating to prevent corrosion, in rechargeable batteries and as a pigment in certain plastics and paints. Special care is taken in the industrial smelting of ores and subsequent handling of cadmium, because occupational exposure is known to have caused heart, chest and kidney disorders. Environmental health problems have come from exposure to various sources of pollution. cadmium |
A hard grey metallic element that takes a high polish, occurring principally in chromite: used in steel alloys and electroplating to increase hardness and corrosion-resistance. chrome |
A metallic element used chiefly in alloys. cobalt |
| A chemical element; one of the most important nonferrous metals; a ductile and malleable metal found in various ores and used in industry, engineering, and the arts in both pure and alloyed form. cuivre |
| A malleable ductile silvery-white ferromagnetic metallic element occurring principally in haematite and magnetite. It is widely used for structural and engineering purposes. fer |
A heavy silvery-white toxic liquid metallic element occurring principally in cinnabar: used in thermometers, barometers, mercury-vapour lamps, and dental amalgams. mercure |
A malleable ductile silvery-white metallic element that is strong and corrosion-resistant, occurring principally in pentlandite and niccolite: used in alloys, especially in toughening steel, in electroplating, and as a catalyst in organic synthesis. nickel |
A ductile malleable silvery-white metallic element very resistant to heat and chemicals. It occurs free and in association with other platinum metals, especially in osmiridium; used in jewellery, laboratory apparatus, electrical contacts, dentistry, electroplating, and as a catalyst. platine |
A strong malleable white metallic element, which is very corrosion-resistant and occurs in rutile and ilmenite. It is used in the manufacture of strong lightweight alloys, especially aircraft parts. titane |
A silvery-white, ductile metal resistant to corrosion; used in alloy steels and as an x-ray target. vanadium |
| A brittle bluish-white metallic element that becomes coated with a corrosion-resistant layer in moist air and occurs chiefly in sphalerite and smithsonite. It is a constituent of several alloys, especially brass and nickel-silver, and is used in die-casting, galvanizing metals, and in battery electrodes. zinc |
élément de transition
One of a group of metallic elements in which the members have the filling of the outermost shell to 8 electrons interrupted to bring the penultimate shell from 8 to 18 or 32 electrons; includes elements 21 through 29 (scandium through copper), 39 through 47 (yttrium through silver), 57 through 79 (lanthanum through gold), and all known elements from 89 (actinium) on.
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