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Scandium

From Academic Kids

calciumscandiumtitanium
Sc
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Image:Sc-TableImage.png
General
Name, Symbol, Numberscandium, Sc, 21
Chemical series transition metals
Group, Period, Block3, 4, d
Density, Hardness 2985 kg/m3, U/K
Appearance Silvery white
Missing image
Sc,21.jpg


Atomic properties
Atomic weight 44.955910 amu
Atomic radius (calc.) 160 (184) pm
Covalent radius 144 pm
van der Waals radius no data
Electron configuration [Ar]3d1 4s2
e- 's per energy level2, 8, 9, 2
Oxidation states (Oxide) 3 (weak base)
Crystal structure Hexagonal
Physical properties
State of matter Solid (__)
Melting point 1814 K (2806 ?F)
Boiling point 3103 K (5126 ?F)
Molar volume 15.00 ×10-6 m3/mol
Heat of vaporization 314.2 kJ/mol
Heat of fusion 14.1 kJ/mol
Vapor pressure 22.1 Pa at 1812 K
Speed of sound no data m/s at 293.15 K
Miscellaneous
Electronegativity 1.36 (Pauling scale)
Specific heat capacity 568 J/(kg*K)
Electrical conductivity 1.77 106/(m·ohm)
Thermal conductivity 15.8 W/(m*K)
1st ionization potential 633.1 kJ/mol
2nd ionization potential 1235.0 kJ/mol
3rd ionization potential 2388.6 kJ/mol
4th ionization potential 7090.6 kJ/mol
5th ionization potential 8843 kJ/mol
6th ionization potential 10679 kJ/mol
7th ionization potential 13310 kJ/mol
8th ionization potential 15250 kJ/mol
9th ionization potential 17370 kJ/mol
10th ionization potential 21726 kJ/mol
Most stable isotopes
isoNAhalf-life DMDE MeVDP
45Sc100%Sc is stable with 24 neutrons
46Sc{syn.}83.79 daysβ-2.36746Ti
SI units & STP are used except where noted.

Scandium is a chemical element in the periodic table that has the symbol Sc and atomic number 21. A soft, silvery, white transition element, scandium occurs in rare minerals from Scandinavia and it is sometimes classified along with yttrium and the lanthanides as a rare earth.

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Contents

Notable characteristics

Scandium is a rare, soft, silvery, trivalent, very light metallic element that develops a slightly yellowish or pinkish cast when exposed to air. This element resembles yttrium and rare earth metals more than it resembles aluminium or titanium (which are closer on the periodic table). The most common oxidation state of scandium is +3 and this metal is not attacked by a 1:1 mixture of HNO3 and 48% HF.

Applications

Approximately 20 kg (as Sc2O3) of scandium are used annually in the United States to make high-intensity lights. Scandium iodide added to mercury-vapor lamps produces a highly efficient artificial light source that resembles sunlight and allows good color reproduction with TV cameras. About 80 kg of scandium is used in lightbulbs globally per year. The radioactive isotope Sc-46 is used in oil refinery crackers as a tracing agent. The main application by volume is in aluminium-scandium alloys for the aerospace industry and for sports equipment (bikes, baseball bats, etc.) which rely of high performance materials. When added to aluminium, scandium can produce improvements in strength (at ambient and elevated temperature), ductility, aging response and grain refinement through the formation of the Al3Sc phase. Furthermore, it has been shown to reduce solidification cracking during the welding of high strength Al alloys.

History

Dmitri Mendeleev used his periodic law, in 1869, to predict the existence and some properties of three unknown elements including one he called ekaboron .

Lars Fredrick Nilson and his team, apparently unaware of that prediction in the spring of 1879, were looking for rare earth metals; using spectrum analysis he found a new element within the minerals euxenite and gadolinite. He named it Scandium, from the Latin Scandia meaning "Scandinavia", and by way of isolating the element he processed 10 kilograms of euxenite with other rare-earth residues, obtaining about 2 grams of very pure scandium oxide (Sc2O3).

Per Teodor Cleve concluded that scandium corresponded well to the hoped-for ekaboron, and notified Mendeleev of this in August.

Metallic scandium was prepared for the first time in 1937, by electrolysis of a eutectic melt of potassium, lithium, and scandium chlorides at 700 to 800° C. Tungsten wire in a pool of liquid zinc were the electrodes in a graphite crucible. The first pound of 99% pure scandium metal wasn't produced until 1960.

Occurrence

Rare minerals from Scandinavia and Malagasy such as thortveitite, euxenite and gadolinite are the only known concentrated sources of this element (which is never found as a free metal).

Element 21 is the 23rd most abundant element in the sun and similar stars but on earth it is only the 50th most abundant element. Scandium is distributed widely on earth, occurring in trace quantities in over 800 minerals. The blue color of the aquamarine variety of beryl is thought to be caused by scandium. It is an important part of the rare mineral thortveitite and is found in residues that remain after tungsten is extracted from Zinnwald wolframite.

Thortveitite is the primary source of scandium with uranium mill tailings by-products also being an important source. Pure scandium is commercially produced by reducing scandium fluoride with calcium metal.

The main source source of scandium is from military stockpiles from the former Soviet Union, which were themselves extracted from uranium tailings. There is no primary production in the Americas or Europe.

Isotopes

Naturally occurring scandium is composed of 1 stable isotope Sc-45. 13 radioisotopes have been characterized with the most stable being Sc-46 with a half-life of 83.79 days, Sc-47 with a half-life of 3.3492 days, and Sc-48 with a half-life of 43.67 hours. All of the remaining radioactive isotopes have half-lifes that are less than 4 hours and the majority of these have half lifes that are less than 2 minutes. This element also has 5 meta states with the most stable being Scm-44 (t? 58.6 h).

The isotopes of scandium range in atomic weight from 39.978 amu (Sc-40) to 53.963 amu (Sc-54). The primary decay mode before the only stable isotope, Sc-45, is electron capture and the primary mode after is beta emission. The primary decay products before Sc-45 are element 20 (calcium) isotopes and the primary products after are element 22 (titanium) isotopes.

Precautions

Scandium metal powder is combustible and presents a fire hazard.

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References

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