What is Boron?
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.
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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.
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Properties of Boron
Some chemical properties, along with the physical properties of boron, are as follows.
The melting point of boron is 2365 K, and the boiling point of the boron is 4275 K.
The atomic mass of boron is 10.811 u, and the electronic configuration is 1s2 2s2 2p1.
Its electronegativity is 2.04, and ionisation Potential is – 8.298 eV.
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).
There are two naturally occurring and stable isotopes of boron, i.e. 11B (80.1%) and 10B (19.9%).
When it undergoes halogenation, the product formed is trihalides. The reaction with bromine is given below.
2B + 3Br2 → 2BBr3
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.
FAQs on Boron
1. What is Boron and where is it typically found in nature?
Boron is a chemical element with the symbol B and atomic number 5. It is not found freely in nature as an element. Instead, it exists combined in compounds such as borax, kernite, and colemanite. These minerals are often found in dried-up lake beds and desert regions, with major deposits located in Turkey and the United States.
2. Is Boron classified as a metal, non-metal, or metalloid?
Boron is classified as a metalloid. This means it has properties that are in between those of metals and non-metals. For example, it is a poor electrical conductor at room temperature but becomes a good conductor at high temperatures, which is a characteristic of semiconductors.
3. What are some of the most important uses of Boron and its compounds?
Boron and its compounds have a wide range of applications. Some key uses include:
- Borosilicate glass: Used for durable cookware and lab equipment because it resists heat shock.
- Nuclear reactors: Boron is excellent at absorbing neutrons, so it is used in control rods to regulate nuclear fission.
- Antiseptics: Boric acid has mild antiseptic properties and is used in eye drops and ointments.
- Super-hard materials: Boron carbide is one of the hardest known substances, used in tank armour and bulletproof vests.
- Agriculture: Boron is an essential micronutrient for plant growth and is added to fertilisers.
4. Why does Boron behave so differently from other elements in its group, like Aluminium?
Boron shows anomalous behaviour primarily due to its exceptionally small size and high ionisation enthalpy compared to other Group 13 elements. Furthermore, it lacks d-orbitals in its valence shell. These factors prevent it from forming metallic bonds like aluminium, causing it to form strong, stable covalent networks instead. This explains its high melting point and non-metallic character.
5. What is the Borax Bead Test and how does it help identify certain metals?
The Borax Bead Test is a qualitative analysis method used in chemistry to identify certain metal ions. When borax (Na₂B₄O₇·10H₂O) is heated on a platinum wire loop, it swells and then fuses into a clear, colourless glassy bead of sodium metaborate and boric anhydride. When this hot bead is dipped in a metal salt and reheated, it forms a characteristically coloured bead. For example, a copper salt will produce a blue bead.
6. How can boric acid be an acid if it doesn't donate a proton (H+)?
This is a great question that points to a key concept. Boric acid (H₃BO₃) is not a typical acid that releases its own proton. Instead, it acts as a weak Lewis acid. It accepts a pair of electrons from a hydroxide ion (OH⁻) from a water molecule. This process releases a proton (H⁺) from the water molecule into the solution, making the solution acidic. So, it increases the H⁺ concentration without donating its own proton.
7. Why are compounds like boron nitride and boron carbide extremely hard?
The extreme hardness of compounds like boron nitride (BN) and boron carbide (B₄C) comes from their atomic structure. They form giant covalent network lattices, similar to the structure of a diamond. In these structures, each atom is bonded to its neighbours by strong, directional covalent bonds, creating a rigid and stable three-dimensional network that is very difficult to break apart.
8. What are boranes, and why are they described as electron-deficient?
Boranes are compounds made of boron and hydrogen, with the simplest example being diborane (B₂H₆). They are called electron-deficient because there are not enough valence electrons to form conventional two-centre, two-electron bonds between all the adjacent atoms. To achieve stability, boranes form unique bonds, such as the three-centre, two-electron bonds (often called 'banana bonds'), where two electrons are shared among three atoms.
