[Chemistry Class Notes] on Boron Pdf for Exam

Boron is an element of chemistry that has atomic number 5. The chemical symbol of elemental boron is  B. It is dark in colour, brittle, lustrous metalloid in its crystalline form on the other side; when it is amorphous boron, it is found in powder form coloured in brown. It is one of the lightest elements as it has only five electrons, and the nucleus is composed of a total of six neutrons and five protons. It has three electrons that used to be present in the valence shells and took part in the formation of covalent bonds, resulting in many compounds such as boric acid, the mineral borax, and boron carbide.

Atomic Structure of Boron

The atomic number of the boron element is 5. The nucleus of this atom consists of six neutrons and five positively charged protons. Five electrons occupy available electron shells and revolve around the nucleus. The stability of the valence electrons determines the chemical and physical properties of the element. Boron is a metalloid that is placed in period 2, group 13 and the p-block of the periodic table.

                                     

Properties of Boron

Some chemical properties, along with the physical properties of boron, are as follows.

1. The melting point of boron is 2365 K, and the boiling point of the boron is 4275 K.

2. The atomic mass of boron is 10.811 u, and the electronic configuration is 1s2 2s2 2p1.

3. Its electronegativity is 2.04, and ionisation Potential is – 8.298 eV. 

4. The boron’s oxidation rate depends on the size of the particle, its crystallinity, temperature and purity. At room temperature, any reaction does not occur with air, but when the temperature reaches, it burns and forms  B2O3 (boron trioxide).

5. There are two naturally occurring and stable isotopes of boron, i.e. 11B (80.1%) and 10B (19.9%).

6. When it undergoes halogenation, the product formed is trihalides. The reaction with bromine is given below.

1. 2B + 3Br2 → 2BBr3

7. Boron in crystalline form is a chemically inert and resistant substance that can be attacked by boiling hydrofluoric or hydrochloric acid. It is attacked slowly by hot concentrated hydrogen peroxide, the hot mixture of sulphuric and chromic acids as well as hot concentrated nitric acid when divided finely.

Occurrence of Boron

Because of the formation of traces in the Big Bang and stars in the solar system, boron is rare in the universe. In small amounts, it is formed in cosmic radiation spallation nucleosynthesis and may be found in the form of uncombined in the dust of cosmic and materials of meteoroids. It is always found fully oxidised to borate in the environment of high oxygen of the Earth. It does not appear on the earth in the form of an element. In the Lunar regolith, minor traces of elemental boron have been detected.

It is a rare element in the crust of the Earth. It occurs naturally in compounds such as borax and boric acid. It is observed that around a hundred borate minerals are known.

Boron is found as an orthoboric acid in some spring waters of volcanoes, and as borates in minerals such as borax and colemanite. Extensive borax deposits are present in Turkey. However, rasorite is the most important source of boron which is present in the Mojave Desert in California, the United States of America.

Use of Boron

Compounds of boron, such as boric acid, borates, boron citrate, borazine etc., are useful in daily life and chemical industries. Some of the uses of boron are given below.

• Boric acid is known by different names such as orthoboric acid, hydrogen borate and boracic acid. It is a weak, monobasic Lewis acid of boron that is widely used as eye lotions, antiseptic for minor burns or cuts and food preservatives. In 1948, It was first registered in the United States as an insecticide for the control of many insects.  

• Boron is used in pyrotechnics to stop the reaction of the formation of amide between aluminium and nitrates.

• Borax is an important compound of boron that is used as a cleansing agent, in a borax bead test and in medical soaps. 

• Borates are taken in the application for brighteners in washing powder and a bleaching agent.  

• In order to grow nanotubes, boron nitride is used as a lubricant.

• Borazine is used for the formation of explosives which is based on carbon.

• It is also used in the manufacturing of ceramics and glass.

Do you know?

• Pure boron is found in the form of dark amorphous powder.

• Boron has the highest melting point as well as the highest boiling point of the metalloids.

• Boron medicine is used for building strong bones.

Conclusion

Boron is a light element that is used for a variety of applications in our daily life. Colemanite, rasorite (kernite) and ulexite are some of the important economic sources of boron. These minerals together contribute around 90 percent of mined ore that contains boron. After going through the article, we get all the important information related to the boron element, such as its chemical and physical properties, occurrence and use of boron etc.