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Scandium                                                                                                                                    

Standard Sate: solid at 298 K

Color:  silvery white

Scandium is apparently a much more abundant element in the sun and certain stars than on earth.Scandium is a silvery-white metal which develops a slightly yellowish or pinkish cast upon exposure to air. It is relatively soft, and resembles yttrium and the rare-earth metals more than it resembles aluminium or titanium. Scandium reacts rapidly with many acids.

(Sm), chemical element, rare-earth metal of transition Group IIIb of
the periodic table. Samarium is silvery white in colour and is
relatively stable in air. It was isolated as an impure oxide and
spectroscopically identified as a new element (1879) by P.-�. Lecoq
de Boisbaudran. Samarium occurs in many other rare-earth minerals
but is almost exclusively obtained from monazite; it is also found in the
products of nuclear fission. Ion-exchange techniques are used for its
commercial separation and purification. The metal is conveniently
prepared by the thermoreduction of its oxide, Sm2O3, with lanthanum
metal, followed by distillation of the samarium metal, which is one of
the most volatile rare-earth elements. Several allotropes (structural
forms) of samarium exist; at room temperature its structure is
rhombohedral.

Because of its high absorption cross section for thermal neutrons,
samarium has been suggested for application in nuclear reactor
control rods and for neutron shielding. Other uses are in special
luminescent and infrared-absorbing glasses, in inorganic and organic
catalysis, and in the electronics and ceramics industries. Samarium is
a minor constituent of misch metal (a mixture of cerium and other
rare-earth metals, used in ferrous and nonferrous alloys).

The seven naturally occurring isotopes of samarium are
samarium-144 (3.1 percent), samarium-147 (15.0 percent),
samarium-148 (11.3 percent), samarium-149 (13.8 percent),
samarium-150 (7.4 percent), samarium-152 (26.7 percent), and
samarium-154 (22.7 percent). Samarium-144, samarium-150,
samarium-152, and samarium-154 are stable, but the other three
naturally occurring isotopes are alpha emitters.

In addition to its more stable trivalent state, samarium, unlike most of
the rare earths, has a +2 oxidation state. The Sm2+ ion is a powerful
reducing agent that rapidly reacts with oxygen, water, or hydrogen
ions. It can be stabilized by precipitation as the extremely insoluble
sulfate SmSO4. Other samarium(II) salts are SmCO3, SmCl2, SmBr2,
and Sm(OH)2; they are reddish brown in colour. Trivalent samarium
behaves as a typical rare-earth element; it forms a series of yellow
salts in solutions. atomic number 62 atomic weight 150.36 melting
point 1,074 C boiling point 1,794 C density 7.520 (25 C) valence 2, 3
electronic config. 2-8-18-24-8-2 or (Xe)4f 65d06s2

"samarium" Encyclop�dia Britannica Online.

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