Boron is the fifth facet of the periodic table (Z=5), located in group 13. That is classified together a metalloid due it its properties the reflect a combination of both metals and nonmetals.

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Introduction

The name Boron comes from the Arabic and Persian words because that borax, its principal ore. Back compounds that boron were known in ancient times, the was very first isolated in 1808 by Gay-Lussac and Thénard and also independently by teacher Humphry Davy (who has a lot of elements to his credit!).

Boron exists in the earth"s crust come the level of only about 10 ppm (about the exact same abundance as lead). The pure element is shiny and black. It is an extremely hard and in extremely pure type is virtually as hard as diamond, yet much too brittle for useful use. In ~ high temperatures it is a good conductor but at room temperature and also below is an insulator. This behavior and many of its various other properties earn it the group of a metalloid. In enhancement to the crystalline kind of boron over there is also an amorphous dark brown powder (as displayed above).

The element can be prepared by the palliation of borax ((Na_2B_4O_7)) with carbon. High-purity boron have the right to be created by electrolysis that molten potassium fluoroborate. Usual compounds of boron include borax and also boric acid ((H_3BO_3)).

Atomic Mass10.811 g/mol
Electronic Configuration2s2 2p1
Melting Point2349 K
Boiling Point4200 K
Heat of Fusion50.2 kJ/mol
Heat the Vaporization480 kJ/mol
Specific warm Capacity11.087 J/mol·K
Oxidation States+4, +3, +2, +1
Magnetic Orderingdiamagnetic
Electronegativity2.04
Atomic Radius90 pm
Stable Isotopes10B, 11B

Boron is the only facet in team 3 the is no a metal. It has properties the lie between metals and also non-metals (semimetals). For instance Boron is a semiconductor unlike the remainder of the group 13 elements. sdrta.netically, that is closer to aluminum than any of the other group 13 elements.


History

Boron was very first discovered through Joseph-Louis Gay-Lussac and Louis-Jaques Thenard, and also independently by Humphry Davy in the year 1808. This sdrta.netists diverted Boron by combine boric acid v potassium. Today, there are many ways that obtaining Boron yet the most common way is by heating borax (a compound of sodium and also boron) with calcium.


Boron and also its Compounds

Many boron compounds are electron-deficient, an interpretation that they lack an octet of electrons roughly the central boron atom. This deficiency is what accounts because that boron being a solid Lewis acid, in that it deserve to accept protons (H+ ions) in solution. Boron-hydrogen compounds are described as boron hydrides, or boranes.

Boranes

In the molecule BH3, every of the 3 hydrogen atoms is bonded to the central boron atom. The boron atom has only 6 electrons in its external shell, resulting in an electron deficiency.

Diborane:

H H

ns I

H - B ? B - H

i I

H H

This molecule has 12 valence shell electrons; 3 every from the B atoms, and 1 each from the 6 H atoms. To make this structure follow the rules compelled to draw any lewis structure model, then it must have 14 valence covering electrons; yet it walk not. According to this figure, the two B atoms and also four H atom lie in the same aircraft (sp3- perpendicular come the aircraft of the page). In these four bonds 8 electrons space involved. 4 electrons bond the remaining H atoms to the two B atoms and the B atom together. This is done as soon as the 2 H atoms concurrently bond come the 2 B atoms. This create what is referred to as an atom "bridge" due to the fact that there are two electrons shared among three atoms. These bonds are likewise called three-center two-electron bonds. The bond between the H and the B atoms have the right to be rationalized using molecular orbit theory.


Other Boron Compounds

Although boron compounds are widely dispersed in Earth"s crust, a few concentrated ores are located in Italy, Russia, Tibet, Turkey, and also California. Borax is the most typical ore found, and also it deserve to be turned right into a selection of boron compounds. As soon as a solution of borax and hydrogen peroxide is crystallized, salt perborate (NaBO3 * 4 H2O) is formed. Sodium perborate is used in color-safe bleaches. The crucial to the bleaching capacity of this link is the existence of its two peroxo teams that leg the boron atom together. One more compound that various other boron compounds deserve to be synthesized indigenous is boric mountain (B(OH)3). When combined with water, the weakly acidic and also electron deficient boric mountain accepts one OH- ion native water and forms the complicated ion -.

Borate salt produce simple solutions that are offered in cleaning agents. Boric acid is additionally used together an insecticide to kill roaches, and also as one antiseptic in eyewash solutions. Other boron compounds are supplied in a variety of things, because that example: adhesives, cement, disinfectants, fertilizers, fire retardants, glass, herbicides, metallurgical fluxes, and also textile bleaches and also dye.


References

Adair, Rick, ed. Boron. The Rosen team Inc., 2007. Print.Hasan, Heather. The Boron Elements: Boron, Aluminum, Gallium, Indium, Thallium. Rosen Group, 2009. Print.

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Problems

What is the electronic configuration that boron?What accounts for the formation of boron hydrides?What room some offers of boron compounds?Draw B4H10.What is the molecular orbit theory and also how is it offered to rationalize the binding in boron hydrides?

Answers

2s2 2p1Boron is highly electronegative, and also wants to form compounds with hydrogen atoms.Adhesives, cement, disinfectants, fertilizers, etc.b4h10.pnghow many valence electrons does boron (b atomic no. = 5) have?