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Boron Element

 

Boron mine at first glance resembles a white rock. It is very hard and heat resistant and is not found as a free element in nature due to its high chemical affinity to other elements, but in the form of compounds with other elements, in the form of salt. There are about 230 kinds of boron minerals in nature. Due to its tendency to bond with oxygen, there are numerous boron-oxygen compounds. The general name of boron oxide compounds is borate. 

Boron mines are made ready for use after crushing, sieving, washing and grinding processes after they are extracted from the soil (Crude ore).

Boron is a black colored semiconductor element between metal and nonmetal having the atom number 5, atomic weight 10.81, density 2.84 g / cm3, melting point 2,200 oC and boiling point 2,250 oC, indicated with the symbol “B" in the periodic table. 

It is the first and lightest member of the periodic table 3A group. The basic state electron configuration is 1s2 2s2 2p1.

The boron element is composed of isotopes 8B, 10B, 11B, 12B, 13B. The most stable isotopes are 10B and 11B. The availability of these isotopes in nature is 19.1-20.3% and 79.7-80.9%, respectively. The isotope 10B shows very high thermal neutron retention. Thus, it can be used in nuclear materials and nuclear power plants.

In our country, there are boron ore deposits with high isotope ratio of 10B.

The various properties of the compounds made by boron with various metal and nonmetal elements allow the use of many kinds of boron compounds in the industry. Among the industrially important boron compounds, borax (tincal, boron compounds of sodium origin) colemanite (calcium boron compounds), ulexite (sodium calcium boron compounds) under the main grouping kernite, probertite, szyabelite, datolite, cacolite, borax pentahydrate, borax pentahydrate , anhydrous borax, boric acid, sodium per borate, anhydrous boric acid, hydroboracid may be listed. The value of boron mines is generally measured by the B2O3 (boron oxide) and those having high level of B2O3 compound are considered more valuable.

Boron act as non-metal compounds in compositions but divergently, pure boron is electrically conductive like carbon. Crystalline boron is similar to diamond in terms of appearance and optical properties  and is almost as hard as diamond.

The pure substance of boron was obtained for the first time by the French chemist J.L. Gay-Lussac and Baron L.J. Thenard and British chemist H. Davy in 1808.

Boron is present in various allotropic forms, including one amorphous and six crystalline polymorphs. Alpha and beta rhombohedral forms are the most studied crystalline polymorphs. The alpha rhombohedral structure deteriorates above 1,200 ° C and a beta rhombohedral form occurs at 1,500 ° C. The amorphous form is converted to beta rhombohedrals above about 1,000 0C, and when any pure boron is heated above the melting point and recrystallized, it becomes beta rhombohedral.

The chemical properties of the boron element depend on the morphology and grain size. Amorphous boron of micron size reacts easily and sometimes violently, while crystalline boron does not react easily. Boron reacts with water at high temperature to form boric acid and some other products. The reaction with mineral acids can be slow or explosive depending on the concentration and temperature, and the main product consists of boric acid and some other products.

Atomic structure, chemical and physical properties of boron are given below.

Atomic Structure of Boron: 

 

 

Atomic Diameter

1.17 Å

 

Atomic Volume

4.6 cm3/mole

 

Crystal Structure

Rhombohedral

 

Electron Configuration

1s2 2s2p1

 

Ionic Diameter

0.23 Å

 

Electron Number (neutral)

5

 

Number of Neutrons

6

 

Number of Protons

5

 

Valance Electrons

2s2p1

 

 Chemical Properties of Boron :

 

 

Electrochemical Equivalent

0.1344 g/amp-hr

 

Electronegative (Pauling)

2.04

 

Fusion Heat

50.2 kJ/mol

 

Ionization Potential

First: 8.298

Second: 25.154

  Third: 37.93

 

Valance Electron Potential (-eV)

190

 

 

Physical Properties of Boron :

 

Atomic Mass:

10.811

Boiling Point:

4275 K - 4002°C - 7236°F

Thermal Expansion Coefficient:

0.0000083 cm/cm/°C (0°C)

Conductivity:

Electrical:  1.0E -12 106/cm

Thermal:  0.274 W/cmK

Density:

2.34 g/cc @ 300K

Appearance:

Yellow-Brown Nonmetallic Crystal

Elastic Modulus

Bulk: 320/GPa

Enthalpy of Atomization

573.2 kJ/mole @ 25°C

Enthalpy of Fusion

22.18 kJ/mole

Enthalpy of Vaporization

480 kJ/mole

Hardness

Mohs:  9.3

Vickers:  49000 MN m-2

Heat of Vaporization

489.7kJ/mol

Melting Point

2573 K - 2300°C - 4172°F

Molar Volume

4.68 cm3/mole

Physical State

(20°C & 1 atm): Solid

Specific Heat

1.02 J/gK

Vapour Pressure

0.348 Pa@2300°C

 
 
 
 
 
 
 
 

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