- Boron (B) is a metalloid with atomic number 5, positioned at the top of Group 13 in the periodic table. It exhibits properties of both metals and nonmetals, which gives it a unique chemical behavior.
- Boron’s atomic structure consists of five protons, typically six neutrons, and five electrons arranged in two shells (two in the inner shell and three in the outer shell). It has three valence electrons, allowing it to form a wide range of covalent compounds.
- In nature, boron occurs almost entirely as two stable isotopes: boron-10 (¹⁰B) and boron-11 (¹¹B), with boron-11 making up about 80% of natural boron.
- The element is never found in pure form in nature; instead, it occurs in compounds such as borax (Na₂B₄O₇·10H₂O), kernite, colemanite, and ulexite.
- Boron is relatively rare in the universe, produced mainly in small amounts through cosmic ray spallation, similar to beryllium and lithium, since it is neither synthesized in significant amounts during Big Bang nucleosynthesis nor formed in stellar fusion processes.
- On Earth, boron is concentrated in evaporite deposits in arid regions, where ancient seas or lakes once existed. Large reserves are found in Turkey, the United States (California), Argentina, and Chile. The element’s occurrence in minerals is closely tied to geological processes that involve the evaporation of boron-rich water.
- The discovery of boron took place in 1808, when it was independently isolated by French chemists Joseph Louis Gay-Lussac and Louis Jacques Thénard, and by English chemist Sir Humphry Davy. Gay-Lussac and Thénard produced impure boron by reducing boric acid with potassium, while Davy used electrolysis to achieve a similar result. The name “boron” is derived from borax, one of its primary mineral sources, whose name in turn originates from the Arabic buraq and Persian burah.
- Boron’s properties and compounds are exceptionally diverse. In its crystalline form, boron is extremely hard—only slightly softer than diamond—and has a high melting point (about 2076 °C). Amorphous boron is a dark brown powder used in pyrotechnics as an ignition source. Boron compounds, such as borosilicate glass (Pyrex), are valued for their resistance to thermal shock, making them ideal for laboratory glassware and cookware. Boron nitride, which exists in hexagonal and cubic forms, is used as a lubricant, an insulator, and even as an abrasive rivaling diamond in hardness. In metallurgy, small amounts of boron are added to steel to significantly increase hardness without affecting ductility.
- Boron has important roles in nuclear science and technology. The isotope ¹⁰B has a high neutron absorption cross-section, making it essential for neutron shielding and control rods in nuclear reactors. It is also used in boron neutron capture therapy (BNCT), an experimental form of cancer treatment. In agriculture, boron is a micronutrient vital for plant growth, involved in cell wall formation and reproductive development, though excessive boron in soil can be toxic.
- While boron is non-toxic in small amounts, occupational exposure to high concentrations of boron-containing dust or fumes can cause irritation to the eyes, skin, and respiratory tract. Careful handling is required in industrial environments, especially in glass manufacturing, ceramics production, and metallurgy.
