ලෝකයේ ඝනත්වය වැඩීම මුලද්‍රව්‍ය ඔස්මියම්

2025/2026/2027 AL Chemistry සිංහල මාධ්‍ය හා English Medium වැඩි විස්තර 0712006784(Whatsapp) මගේ අලුත්ම channel එකේ video එක    • Video 02 : මැණික් ස්ඵටික වල විද්‍යාත්මක පස...   Osmium (chemical symbol: Os, atomic number: 76) is a remarkable element in the platinum group metals, renowned for several extraordinary properties. Here's a detailed description of osmium: 1. Physical Characteristics: Appearance: Crystalline osmium exhibits a distinctive bluish-white or bluish-silver luster. Density: It is the densest naturally occurring element, with a density of approximately 22.59 g/cm 3 . To put this into perspective, it's about twice as dense as lead. This extreme density arises from its heavy atomic mass and tightly packed atomic structure. Hardness: Osmium is a very hard metal, with a Mohs hardness of around 7.0, making it comparable to quartz and harder than many common metals. Brittleness: Despite its hardness, osmium is notably brittle, which makes it challenging to shape, form, or machine into desired objects, especially in its pure solid form. Melting and Boiling Points: It possesses exceptionally high melting (3033 °C) and boiling (5012 °C) points. It has the highest melting point among the platinum group metals and the fourth highest among all elements. Compressibility: Osmium has very low compressibility and an extremely high bulk modulus, which is a measure of its resistance to compression. This property rivals that of diamond. 2. Chemical Properties: Reactivity: While elemental osmium is relatively unreactive, particularly in bulk form, its powdered form can react with oxygen in the air to form osmium tetroxide. Oxidation States: Osmium exhibits a wide range of oxidation states, from -4 to +8. The +8 oxidation state is particularly noteworthy, being one of the highest known for any element (shared with ruthenium, xenon, and hassium, with iridium recently shown to have a +9 state under specific conditions). This allows it to form diverse compounds. Compounds: The most significant compound is osmium tetroxide (OsO 4 ​ ). This compound is a volatile, pale yellow crystalline solid with a strong, unpleasant, chlorine-like odor. It's also highly toxic. 3. Rarity and Occurrence: Osmium is one of the rarest elements in the Earth's crust. It is typically found in trace amounts within platinum ores and other platinum group metal deposits. Its scarcity contributes to its high cost. 4. Discovery: Osmium was discovered in 1803 by the English chemist Smithson Tennant in London. He identified it in the residue left after dissolving crude platinum ore in aqua regia (a potent mixture of nitric and hydrochloric acids). Its name is derived from the Greek word "osme," meaning "smell," due to the pungent odor of its volatile oxide. 5. Toxicity: Elemental osmium is generally considered non-toxic. However, osmium tetroxide (OsO 4 ​ ) is extremely toxic and hazardous. It is highly volatile and its vapors can cause severe irritation and damage to the eyes, skin, and respiratory tract. It can also cause blindness and internal organ damage upon exposure. Due to this toxicity, handling osmium, especially in powdered form or when heated, requires strict safety precautions and good ventilation. Crystalline osmium, when specifically manufactured, can be rendered non-toxic and safe to handle. 6. Applications: Given its unique combination of extreme hardness, density, high melting point, and resistance to wear, osmium finds specialized, albeit limited, applications: Hard Alloys: Its primary use is in very hard and durable alloys, often with other platinum-group metals like platinum and iridium. These alloys are used for: Fountain pen nib tips Electrical contacts (where extreme durability is needed) Instrument pivots (e.g., in watches and scientific instruments) Long-life phonograph needles (historically) Catalysis: Certain osmium compounds act as catalysts in various chemical reactions, particularly in organic synthesis. Electron Microscopy: Osmium tetroxide is used as a staining agent in electron microscopy to enhance the contrast of biological tissues, making cellular structures more visible. Early Lamp Filaments: Historically, osmium was used for incandescent lamp filaments, but it was later replaced by tungsten due to tungsten's superior properties and easier workability. Jewelry and Investment (Crystalline Osmium): More recently, highly pure, crystalline osmium has gained attention in the jewelry and investment markets due to its unique luster, rarity, and as a tangible asset. In summary, osmium is a rare, exceptionally dense, hard, and brittle metal with a distinctive bluish-white appearance. While the elemental form is relatively benign, its volatile oxide, osmium tetroxide, is highly toxic. Its extreme properties make it invaluable for specialized applications requiring ultimate durability and wear resistance.