Rare Earth Elements (Metals) - List

Rare Earth Elements (Metals) - List This is a list of rare earth elements (REEs), which are a special group of metals. Key Takeaways: List of Rare Earth Elements The rare earth elements (REEs) or rare earth metals (REMs) are a group of metals found within the same ores and possessing similar chemical properties.Scientists and engineers disagree on exactly which element should be included in a list of the rare earths, but they generally include the fifteen lanthanide elements, plus scandium and yttrium.Despite their name, the rare earths arent actually rare with respect to abundance in the Earths crust. The exception is promethium, a radioactive metal. The CRC Handbook of Chemistry and Physics and IUPAC list the rare earths as consisting of the lanthanides, plus scandium and yttrium. This includes atomic number 57 through 71, as well as 39 (yttrium) and 21 (scandium): Lanthanum (sometimes considered a transition metal)CeriumPraseodymiumNeodymiumPromethiumSamariumEuropiumGadoliniumTerbiumDysprosiumHolmiumErbiumThuliumYtterbiumLutetiumScandiumYttrium Other sources consider the rare earths to be the lanthanides and actinides: Lanthanum (sometimes considered a transition metal)CeriumPraseodymiumNeodymiumPromethiumSamariumEuropiumGadoliniumTerbiumDysprosiumHolmiumErbiumThuliumYtterbiumLutetiumActinium (sometimes considered a transition metal)ThoriumProtactiniumUraniumNeptuniumPlutoniumAmericiumCuriumBerkeliumCaliforniumEinsteiniumFermiumMendeleviumNobeliumLawrencium Classification of Rare Earths The classification of the rare earth elements is as hotly disputed as the list of included metals. One common method of classification is by atomic weight. Low atomic weight elements are the light rare earth elements (LREEs). Elements with high atomic weight are the heavy rare earth elements (HREEs). Elements that fall between the two extremes are the middle rare earth elements (MREEs). One popular system categorizes atomic numbers up to 61 as LREEs and those higher than 62 as HREEs (with the middle range absent or up to interpretation). Summary of Abbreviations Several abbreviations are used in connection with the rare earth elements: RE: rare earthREE: rare earth elementREM: rare earth metalREO: rare earth oxideREY: rare earth element and yttriumLREE: light rare earth elementsMREE: middle rare earth elementsHREE: heavy rare earth elements Rare Earth Uses In general, the rare earths are used in alloys, for their special optical properties, and in electronics. Some specific uses of elements include: Scandium: Use to make light alloys for the aerospace industry, as a radioactive tracer, and in lampsYttrium: Used in yttrium aluminum garnet (YAG) lasers, as a red phosphor, in superconductors, in fluorescent tubes, in LEDs, and as a cancer treatmentLanthanum: Use to make high refractive index glass, camera lenses, and catalystsCerium: Use to impart a yellow color to glass, as a catalyst, as a polishing powder, and to make flintsPraseodymium: Used in lasers, arc lighting, magnets, flint steel, and as a glass colorantNeodymium: Used to impart violet color to glass and ceramics, in lasers, magnets, capacitors, and electric motorsPromethium: Used in luminous paint and nuclear batteriesSamarium: Used in lasers, rare earth magnets, masers, nuclear reactor control rodsEuropium: Used to prepare red and blue phosphors, in lasers, in fluorescent lamps, and as an NMR relaxantGadolinium: Used in lasers, x-ray tubes, computer memory, high refractive index glass, NMR relaxation, neutron capture, MRI contrast Terbium: Use in green phosphors, magnets, lasers, fluorescent lamps, magnetostrictive alloys, and sonar systemsDysprosium: Used in hard drive disks, magnetostrictive alloys, lasers, and magnetsHolmium: Use in lasers, magnets, and calibration of spectrophotometersErbium: Used in vanadium steel, infrared lasers, and fiber opticsThulium: Used in lasers, metal halide lamps, and portable x-ray machinesYtterbium: Used in infrared lasers, stainless steel, and nuclear medicineLutetium: Used in positron emission tomography (PET) scans, high refractive index glass, catalysts, and LEDs Sources Brownlow, Arthur H. (1996). Geochemistry. Upper Saddle River, N.J.: Prentice Hall. ISBN 978-0133982725.Connelly, N. G. and T. Damhus, ed. (2005). Nomenclature of Inorganic Chemistry: IUPAC Recommendations 2005. With R. M. Hartshorn and A. T. Hutton. Cambridge: RSC Publishing. ISBN 978-0-85404-438-2.Hammond, C. R. (2009). Section 4; The Elements. In David R. Lide (ed.). CRC Handbook of Chemistry and Physics, 89th ed. Boca Raton, FL: CRC Press/Taylor and Francis.JÃ ©brak, Michel; Marcoux, Eric; Laithier, Michelle; Skipwith, Patrick (2014). Geology of mineral resources (2nd ed.). St. Johns, NL: Geological Association of Canada. ISBN 9781897095737.Ullmann, Fritz, ed. (2003). Ullmanns Encyclopedia of Industrial Chemistry. 31. Contributor: Matthias Bohnet (6th ed.). Wiley-VCH. p. 24. ISBN 978-3-527-30385-4.

Learn About the Associative Property in Math

Learn About the Associative Property in Math According to the associative property, the addition or multiplication of a set of numbers is the same regardless of how the numbers are grouped. The associative property will involve 3 or more numbers. The parenthesis indicates the terms that are considered one unit. The groupings (Associative Property) are within the parenthesis. Hence, the numbers are associated together. In multiplication, the product is always the same regardless of their grouping. The Associative Property is pretty basic to computational strategies. Remember, the groupings in the brackets are always done first, this is part of the order of operations. Addition Example of the Associative Property When we change the groupings of addends, the sum does not change:(2 5) 4 11 or 2 (5 4) 11(9 3) 4 16 or 9 (3 4) 16Just remember that when the grouping of addends changes, the sum remains the same. Multiplication Example of the Associative Property When we change the groupings of factors, the product does not change:(3 x 2) x 4 24 or 3 x (2 x 4) 24.Just remember that when the grouping of factors changes, the product remains the same. Think Grouping! Changing the grouping of addends does not change the sum, changing the groupings of factors, does not change the product. Simply put, regardless of whether you show 3 x 4 or 4 x 3, the final result is the same. In addition, 4 3 or 3 4, you know that the outcome is the same, the answer remains the same. However, this is NOT the case in subtraction or division so when you think of the associative property, remember that the final result or answer remains the same or its not the associative property. The understanding of the concept of associative property is much more important that the actual term associative property. Titles often confuse students and youll discover that youll ask what the associative property is, only to be returned with a blank look. However, if you say to a child something like If I change the numbers in my addition sentence, does it matter? In other words, can I say 5 3 and 3 5, will the child that understands say yes because its the same? When you ask if you can do this with subtraction, theyll laugh or tell you that you cant do that. So in essence, a child knows about the associative property which is really all that matters even though you may stump them when you ask for a definition of the associative property. Do I care that the definition escapes them? Not at all, if they indeed know the concept. Lets not trip our students up with labels and definitions when concept understanding is the key ingredient in math.