View source for Boron

'''Boron''' is a [[metalloid]] with symbol '''B''' and atomic number 5.

==Properties==
===Chemical===
Boron's chemical properties are closer to [[silicon]] than to [[aluminium]], the element next in group. Crystalline boron is chemically inert and resistant to attack by hot [[hydrohalic acids]], such as [[hydrochloric acid]] and [[hydrofluoric acid]]. Boron does not react with air at standard conditions, but it burns at high temperatures to form [[boron trioxide]]. Its halides are Lewis acids due to an unfilled valence shell.

Boron-containing compounds can be tested for in solution using curcumin. The normally yellow [[curcumin]] reacts with boron, turning deep red. This test will not work in basic conditions, however, as curcumin is normally red in strongly basic solutions.

===Physical===
Chemically, boron is a metalloid. It is a brown-black solid at standard conditions. It has a very high melting point, 2076 °C and boils at 3927 °C. It's density varies between 2.35 and 2.52 g/cm<sup>3</sup>.

Boron exists as two main allotrope forms:
*'''Amorphous boron''': brown powder, similar in aspect with cocoa powder. This one in turn consists of two forms: '''powder''' (brown-black) and '''glassy''' (opaque black).
*'''Crystalline boron''': black, extremely hard (about 9.5 on the [[Mohs scale]]). It is a poor electrical conductor at room temperature. Crystalline boron also consists of several varieties: α-rhombohedral, α-tetragonal, β-rhombohedral, β-tetragonal. γ-orthorhombic, cubic, high-pressure superconducting and borospherene.<ref>http://en.wikipedia.org/wiki/Allotropes_of_boron</ref> Among these, β-rhombohedral is the most thermodynamically stable allotrope.

==Availability==
Both amorphous and crystalline boron can be bought online. [http://elementsales.com/pl_element.htm#bb Metallium] sells both types, sealed in glass ampoules.

==Preparation==
Elemental boron can be extracted from [[boric acid]], by dehydrating it to [[boron trioxide]] and reducing the oxide with [[magnesium]]. The resulting mass, more of a slag actually is treated with hydrochloric acid to remove the impurities. This part should be done slowly, as the residual [[magnesium diboride]] reacts with HCl to release [[borane]] and [[diborane]] that are pyrophoric. Once the reaction has stopped, filter the black boron powder and dry it.<ref>http://www.youtube.com/watch?v=0QBCyOrjR2o</ref>

==Projects==
*Make boranes and organoboron compounds

==Handling==
===Safety===
Elemental boron, boron oxide, boric acid, [[Borate|borates]], and certain organoboron compounds are non-toxic to humans and animals, but are toxic for insects. Boron halides are corrosive.

===Storage===
No special storage is required.

===Disposal===
Boron poses little toxicity to the environment and can be dumped in the trash.

==References==
<references/>
===Relevant Sciencemadness threads===

[[Category:Elements]]
[[Category:Metalloids]]
[[Category:Reducing agents]]
[[Category:P-block]]