the chemistry of boron and its compounds pdf

The Chemistry Of Boron And Its Compounds Pdf

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It is classified as a metalloid due it its properties that reflect a combination of both metals and nonmetals. The name Boron comes from the Arabic and Persian words for borax, its principal ore. Boron exists in the earth's crust to the extent of only about 10 ppm about the same abundance as lead.

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Bonding with boron

The periodic table is a chart that shows how the chemical elements are related to each other. The elements in this group are usually referred to as the aluminum family. Boron is quite different from other members of the family. One difference is that boron is not a metal. All other members of the family aluminum, gallium, indium, and thallium are metals.

Compounds of boron have been used for centuries. Borax, a boron compound, has long been used to make glass and glazes. The element itself was not identified until The most important use of boron is still in glass manufacture.

Agriculture, fire retardants, and soaps and detergents rely on boron compounds. The first mention of boron compounds is found in a book by Persian alchemist Rhazes c. Alchemists studied the nature of matter before modern chemistry was born.

Rhazes classified minerals into six classes, one of which was the boraces, which included borax. Borax was widely used by crafts people. It reduces the melting point of materials used to make glass. It was also used to melt the ores of metals and to isolate the metals from those ores.

In , English chemist Humphry Davy had just learned how to isolate the most active metals, such as sodium and potassium. He was also working on a method to remove boron from its compounds. See sidebar on Davy in the calcium entry.

News of Davy's success had traveled to France, where emperor Napoleon Bonaparte grew concerned about the scientific reputation of his country. He ordered larger and better equipment built for his scientists. He wanted them to surpass Davy in his work on metals. They heated boracic acid also known as boric acid, H 3 BO 3 with potassium metal to produce impure boron. In , French chemist Henri Moissan produced boron that was 98 percent pure.

The names borax and boracic acid probably originated as far back as the time of Rhazes as buraq in Arabic or burah in Persian. One of the unusual properties of boron is the many physical forms, called allotropes, in which it occurs.

Allotropes are forms of an element with different physical and chemical properties. One form of boron consists of clear red crystals with a density of 2. A second form consists of black crystals with a metallic appearance and a density of 2. Boron can also occur as a brown powder with no crystalline structure. The density of this powder is 2. One property of special importance is boron's ability to absorb neutrons. Neutrons are subatomic particles with no charge that occur in the nucleus of nearly all atoms.

Boron atoms are able to absorb a large number of neutrons. This makes boron useful in the control rods of nuclear reactors. A nuclear reactor is a device for generating energy from nuclear fission reactions. Nuclear fission is the process in which large atoms are split, releasing large amounts of energy and smaller atoms.

In a nuclear reactor, it is essential that just the right number of neutrons are present. Too many neutrons can cause a fission reaction to get out of control. Too few neutrons and a fission reaction stops. Control rods are long tubes packed with boron or some other element. The rods can be raised and lowered in the reactor.

As the rods are lowered into the core, the boron absorbs neutrons, slowing the reaction. Boron combines with oxygen in the air to form boron trioxide B 2 O 3. Boron trioxide forms a thin film on the surface that prevents further reaction with oxygen. Boron is not soluble in water. It normally does not react with acids.

It also dissolves in molten melted metals. The abundance of boron in the Earth's crust is estimated to be about 10 parts per million. That places it in about the middle among the elements in terms of their abundance in the earth. Boron never occurs as a free element but always as a compound. The most common minerals of boron are borax, or sodium borate Na 2 B 4 O 7 ; kernite another form of sodium borate ; colemanite, or calcium borate Ca 2 B 6 O 11 ; and ulexite, or sodium calcium borate NaCaB 5 O 9.

These minerals usually occur as white crystalline deposits in desert areas. The two largest world producers of boron compounds are Turkey and the United States. Smaller amounts come from Argentina and China. R adiation can kill living cells. Light, X rays, radio waves, and microwaves are all forms of radiant energy. These forms of radiation differ from each other in the amount of energy they carry with them.

X rays carry a great deal of energy; light waves, less energy; and radio waves, very little energy. The bad news about high-energy radiation is that it can kill healthy cells. A person exposed to high levels of X rays will become ill and may die. Because the X rays kill so many cells, the person's body cannot survive. Essential body functions stop, and death occurs.

The good news is that high-energy radiation can be used to kill cancer cells. Cancer cells are abnormal cells that reproduce faster than normal tissue. The rapidly dividing cells form tumors, crowd organs, and shut down some organ function. Radiation is one way to kill cancer cells. The problem lies in killing only the cancer cells. The radiation has to be "targeted" at the cancer bad cells, and not the healthy good cells. Scientists think that using boron may be one way of achieving this goal.

A new procedure called boron neutron capture therapy BNCT is one method for targeting cancer cells. With BNCT, a person with cancer receives an injection of boron.

The boron tends to go directly to cancer cells. The patient receives an injection of boron that deposits only in the cancer cells. Scientists currently do not know why boron favors cancer cells. But it does. The patient's body is then bombarded with neutrons that pass through without harming health cells.

They then collide with boron atoms. This causes boron to be converted into lithium atoms, alpha particles, and gamma rays. An alpha particle is a helium atom without electrons. Gamma radiation is very high-energy radiation that can kill cells. The lithium atoms and alpha particles travel only a short distance. They do not leave the cancer cell but have enough energy to kill the cell. Since they do not leave the cell, they pose no threat to healthy cells nearby.

Two naturally occurring isotopes of boron exist: boron and boron Isotopes are two or more forms of an element. Isotopes differ from each other according to their mass number.

The number written to the right of the element's name is the mass number. The mass number represents the number of protons plus neutrons in the nucleus of an atom of the element. The number of protons determines the element, but the number of neutrons Boron alloys are used in magnets in microphones and headphones. Each variation is an isotope. Boron is the isotope with high neutron-absorbing tendencies described earlier under "Physical properties.

Three radioactive isotopes of boron are known also. A radioactive isotope is one that breaks apart and gives off some form of radiation.

Radioactive isotopes are produced when very small particles are fired at atoms. These particles stick in the atoms and make them radioactive. Boric oxide is heated with powdered magnesium or aluminum:. Particle accelerators include magnets that consist of boron alloys. The element can also be obtained by passing an electric current through molten melted boron trichloride:.

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Boron is a non metallic element and the only non-metal of the group 13 of the periodic table the elements. Boron is electron-deficient, possessing a vacant p-orbital. It has several forms, the most common of which is amorphous boron, a dark powder, unreactive to oxygen, water, acids and alkalis. It reacts with metals to form borides. At standard temperatures boron is a poor electrical conductor but is a good conductor at high temperatures.

Chemistry of boron. Unique properties of boron. •Boron and its compounds on burning produces a green colored flame. •Boron isotope has.

Review on the Synthesis and Properties of the Energetic Compound Containing Boron

The periodic table is a chart that shows how the chemical elements are related to each other. The elements in this group are usually referred to as the aluminum family. Boron is quite different from other members of the family.

Chemistry of Boron (Z=5)


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