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calcium scandium titanium
Sc
Y  
 
 
Image:Sc-TableImage.png
General
Name, Symbol, Number scandium, Sc, 21
Chemical series transition metals
Group, Period, Block 3, 4 , d
Density, Hardness 2985 kg/m3, U/K
Appearance Silvery white
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 level 2, 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/(mohm)
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
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.

 

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 of scandium (as Sc2O3) are used annually in the United States to make high-intensity lights. The radioactive isotope Sc-46 is used in oil refinery crackers as a tracing agent. When scandium iodide is added to mercury vapor lamps a highly efficient artificial sunlight-like light source is produced which is used in indoor or night-time color televisions. Approximately 80 kg of scandium is used in lightbulbs globally per year. The main usage by volume is in aluminium-scandium alloys for sporting goods (bikes, baseball bats, etc.) When added to aluminium, it can produce improvements in strength, 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. Sc is thus finding applications in the aerospace and sports equipment industries which rely of high performance Al alloys.

History

Scandium (Latin Scandia meaning "Scandinavia") was discovered by Lars Fredrick Nilson in 1879 while he and his team were looking for rare earth metals. Nilson used spectrum analysis to find the new element within the minerals euxenite and gadolinite. To isolate the element he processed 10 kilograms of euxenite with other rare-earth residues to obtain about 2 grams of very pure scandium oxide (Sc2O3).

Dmitri Mendeleev, in 1869, predicted the existence and some properties of this element, which he called ekaboron, using his periodic law. Per Teodor Cleve discovered scandium oxide at about the same time as Nilson but unlike Nilson, Cleve determined that scandium was identical to ekaboron.

In 1937 metallic scandium was prepared for the first time 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.

References

External links

 

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