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#3 Science HQ » Posassium » 2025-06-17 15:50:25

Jai Ganesh
Replies: 0

Potassium

Gist

Potassium, with the chemical symbol K and atomic number 19, is a soft, silvery-white metal that is a member of the alkali metal group. It is highly reactive and not found naturally in its pure form. Potassium is crucial for plant growth, being a key component in fertilizers, and also plays an essential role in human and animal nutrition.

Potassium is a vital mineral and electrolyte that plays a crucial role in various bodily functions. It helps regulate fluid balance, muscle contractions, nerve signals, and the heartbeat. Most people can obtain sufficient potassium through their diet, with fruits and vegetables being excellent sources.

Summary

Potassium is a chemical element; it has symbol K (from Neo-Latin kalium) and atomic number 19. It is a silvery white metal that is soft enough to easily cut with a knife. Potassium metal reacts rapidly with atmospheric oxygen to form flaky white potassium peroxide in only seconds of exposure. It was first isolated from potash, the ashes of plants, from which its name derives. In the periodic table, potassium is one of the alkali metals, all of which have a single valence electron in the outer electron shell, which is easily removed to create an ion with a positive charge (which combines with anions to form salts). In nature, potassium occurs only in ionic salts. Elemental potassium reacts vigorously with water, generating sufficient heat to ignite hydrogen emitted in the reaction, and burning with a lilac-colored flame. It is found dissolved in seawater (which is 0.04% potassium by weight), and occurs in many minerals such as orthoclase, a common constituent of granites and other igneous rocks.

Potassium is chemically very similar to sodium, the previous element in group 1 of the periodic table. They have a similar first ionization energy, which allows for each atom to give up its sole outer electron. It was first suggested in 1702 that they were distinct elements that combine with the same anions to make similar salts, which was demonstrated in 1807 when elemental potassium was first isolated via electrolysis. Naturally occurring potassium is composed of three isotopes, of which 40K is radioactive. Traces of 40K are found in all potassium, and it is the most common radioisotope in the human body.

Potassium ions are vital for the functioning of all living cells. The transfer of potassium ions across nerve cell membranes is necessary for normal nerve transmission; potassium deficiency and excess can each result in numerous signs and symptoms, including an abnormal heart rhythm and various electrocardiographic abnormalities. Fresh fruits and vegetables are good dietary sources of potassium. The body responds to the influx of dietary potassium, which raises serum potassium levels, by shifting potassium from outside to inside cells and increasing potassium excretion by the kidneys.

Most industrial applications of potassium exploit the high solubility of its compounds in water, such as saltwater soap. Heavy crop production rapidly depletes the soil of potassium, and this can be remedied with agricultural fertilizers containing potassium, accounting for 95% of global potassium chemical production.

Details

Potassium (K), chemical element of Group 1 (Ia) of the periodic table, the alkali metal group, indispensable for both plant and animal life. Potassium was the first metal to be isolated by electrolysis, by the English chemist Sir Humphry Davy, when he obtained the element (1807) by decomposing molten potassium hydroxide (KOH) with a voltaic battery.

Element Properties

atomic number  :  19
atomic weight  :  39.098
melting point  :  63.28 °C (145.90 °F)
boiling point  :  760 °C (1,400 °F)
specific gravity  :  0.862 (at 20 °C, or 68 °F)
oxidation states  :  +1, −1 (rare)

Properties, occurrence, and uses

Potassium metal is soft and white with a silvery lustre, has a low melting point, and is a good conductor of heat and electricity. Potassium imparts a lavender colour to a flame, and its vapour is green. It is the seventh most abundant element in Earth’s crust, constituting 2.6 percent of its mass.

The potassium content of the Dead Sea is estimated at approximately 1.7 percent potassium chloride, and many other salty bodies of water are rich in potassium. The waste liquors from certain saltworks may contain up to 40 grams per litre of potassium chloride and are used as a source of potassium.

Most potassium is present in igneous rocks, shale, and sediment in minerals such as muscovite and orthoclase feldspar that are insoluble in water; this makes potassium difficult to obtain. As a result, most commercial potassium compounds (often loosely called potash) are obtained via electrolysis from soluble potassium compounds, such as carnallite (KMgCl3∙6H2O), sylvite (potassium chloride, KCl), polyhalite (K2Ca2Mg[SO4]4∙2H2O), and langbeinite (K2Mg2[SO4]3), which are found in ancient lake beds and seabeds.

Potassium is produced by sodium reduction of molten potassium chloride, KCl, at 870 °C (1,600 °F). Molten KCl is continuously fed into a packed distillation column while sodium vapour is passed up through the column. By condensation of the more volatile potassium at the top of the distillation tower, the reaction Na + KCl → K + NaCl is forced to the right. Efforts to devise a scheme for commercial electrolytic production of potassium have been unsuccessful because there are few salt additives that can reduce the melting point of potassium chloride to temperatures where electrolysis is efficient.

There is little commercial demand for potassium metal itself, and most of it is converted by direct combustion in dry air to potassium superoxide, KO2, which is used in respiratory equipment because it liberates oxygen and removes carbon dioxide and water vapour. (The superoxide of potassium is a yellow solid consisting of K+and O2− ions. It also can be formed by oxidation of potassium amalgam with dry air or oxygen.) The metal is also used as an alloy with sodium as a liquid metallic heat-transfer medium. Potassium reacts very vigorously with water, liberating hydrogen (which ignites) and forming a solution of potassium hydroxide, KOH.

Sodium-potassium alloy (NaK) is used to a limited extent as a heat-transfer coolant in some fast-breeder nuclear reactors and experimentally in gas-turbine power plants. The alloy is also used as a catalyst or reducing agent in organic synthesis.

In addition to the alloys of potassium with lithium and sodium, alloys with other alkali metals are known. Complete miscibility exists in the potassium-rubidium and potassium-cesium binary systems. The latter system forms an alloy melting at approximately −38 °C (−36 °F). Modification of the system by the addition of sodium results in a ternary eutectic melting at approximately −78 °C (−108 °F). The composition of this alloy is 3 percent sodium, 24 percent potassium, and 73 percent cesium. Potassium is essentially immiscible with all the alkaline-earth metals, as well as with zinc, aluminum, and cadmium.

Potassium (as K+) is required by all plants and animals. Plants need it for photosynthesis, regulation of osmosis and growth, and enzyme activation. Every animal has a closely maintained potassium level and a relatively fixed potassium-sodium ratio. Potassium is the primary inorganic cation within the living cell, and sodium is the most abundant cation in extracellular fluids. In higher animals, selective complexants for Na+ and K+ act at cell membranes to provide “active transport.” This active transport transmits electrochemical impulses in nerve and muscle fibres and in balancing the activity of nutrient intake and waste removal from cells. Too little or too much potassium in the body is fatal; however, potassium in the soil ensures the presence of this indispensable element in food.

The potassium content of plants varies considerably, though it is ordinarily in the range of 0.5–2 percent of the dry weight. In humans the ratio of potassium between the cell and plasma is approximately 27:1. The potassium content of muscle tissue is approximately 0.3 percent, whereas that of blood serum is about 0.01–0.02 percent. The dietary requirement for normal growth is approximately 3.3 grams (0.12 ounce) of potassium per day, but the ingestion of more than 20 grams (0.7 ounce) of potassium results in distinct physiological effects. Excess potassium is excreted in the urine, and a significant quantity may be lost during sweating.

Natural potassium consists of three isotopes: potassium-39 (93.26 percent), potassium-41 (6.73 percent), and radioactive potassium-40 (about 0.01 percent); several artificial isotopes have also been prepared. Potassium-39 is normally about 13.5 times more plentiful than potassium-41. The natural radioactivity of potassium is due to beta radiation from the potassium-40 isotope ({10}^{9} years half-life). The disintegration of potassium-40 is used in geological age calculations (see potassium-argon dating). Potassium easily loses the single 4s electron, so it normally has an oxidation state of +1 in its compounds, although compounds that contain the anion, K−, can also be made.

Additional Information

Potassium is a vital mineral and electrolyte that plays a crucial role in various bodily functions. It helps regulate fluid balance, muscle contractions, nerve signals, and the heartbeat. Most people can obtain sufficient potassium through their diet, with fruits and vegetables being excellent sources.

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#4 Re: Jai Ganesh's Puzzles » General Quiz » 2025-06-17 15:10:01

Hi,

#10421. What does the term in Chemistry Chemical element mean?

#10422. What does the term in Chemistry Ore mean?

#5 Re: Jai Ganesh's Puzzles » English language puzzles » 2025-06-17 14:49:59

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#5609. What does the adjective loathsome mean?

#5610. What does the noun lobby mean?

#6 Re: Jai Ganesh's Puzzles » Doc, Doc! » 2025-06-17 14:16:08

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#2395. What does the medical term Corticomesencephalic tract mean?

#10 Science HQ » Sodium » 2025-06-16 17:57:10

Jai Ganesh
Replies: 0

Sodium

Gist

Sodium, with the symbol Na, is a chemical element, specifically a soft, silvery-white, highly reactive alkali metal. It's atomic number is 11 and its atomic mass is approximately 23. Sodium is essential for maintaining fluid balance, nerve and muscle function, and blood pressure regulation in the body. It is found abundantly in nature, primarily as sodium chloride (common table salt).

Summary

Sodium is a chemical element; it has symbol Na (from Neo-Latin natrium) and atomic number 11. It is a soft, silvery-white, highly reactive metal. Sodium is an alkali metal, being in group 1 of the periodic table. Its only stable isotope is 23Na. The free metal does not occur in nature and must be prepared from compounds. Sodium is the sixth most abundant element in the Earth's crust and exists in numerous minerals such as feldspars, sodalite, and halite (NaCl). Many salts of sodium are highly water-soluble: sodium ions have been leached by the action of water from the Earth's minerals over eons, and thus sodium and chlorine are the most common dissolved elements by weight in the oceans.

Sodium was first isolated by Humphry Davy in 1807 by the electrolysis of sodium hydroxide. Among many other useful sodium compounds, sodium hydroxide (lye) is used in soap manufacture, and sodium chloride (edible salt) is a de-icing agent and a nutrient for animals including humans.

Sodium is an essential element for all animals and some plants. Sodium ions are the major cation in the extracellular fluid (ECF) and as such are the major contributor to the ECF osmotic pressure. Animal cells actively pump sodium ions out of the cells by means of the sodium–potassium pump, an enzyme complex embedded in the cell membrane, in order to maintain a roughly ten-times higher concentration of sodium ions outside the cell than inside. In nerve cells, the sudden flow of sodium ions into the cell through voltage-gated sodium channels enables transmission of a nerve impulse in a process called the action potential.

Details

Sodium (Na) is a chemical element of the alkali metal group (Group 1 [Ia]) of the periodic table. Sodium is a very soft silvery-white metal. Sodium is the most common alkali metal and the sixth most abundant element on Earth, comprising 2.8 percent of Earth’s crust. It occurs abundantly in nature in compounds, especially common salt—sodium chloride (NaCl)—which forms the mineral halite and constitutes about 80 percent of the dissolved constituents of seawater.

Element Properties

atomic number  :  11
atomic weight  :  22.9898
melting point  :  97.81 °C (208 °F)
boiling poin  :  882.9 °C (1,621 °F)
specific gravity  :  0.971 (20 °C)
oxidation states  :  +1, −1 (rare)

Properties and production

Because sodium is extremely reactive, it never occurs in the free state in Earth’s crust. In 1807 Sir Humphry Davy became the first to prepare sodium in its elemental form, applying electrolysis to fused sodium hydroxide (NaOH). Sodium is an important constituent of a number of silicate materials, such as feldspars and micas. There are huge deposits of rock salt in various parts of the world, and sodium nitrate deposits exist in Chile and Peru. The sodium content of the sea is approximately 1.05 percent, corresponding to a concentration of approximately 3 percent of sodium halides. Sodium has been identified in both the atomic and ionic forms in the spectra of stars, including the Sun, and the interstellar medium. Analysis of meteorites indicates that the silicate material present has an average content of approximately 4.6 atoms of sodium for every 100 atoms of silicon.

Lighter than water, sodium can be cut with a knife at room temperature but is brittle at low temperatures. It conducts heat and electricity easily and exhibits the photoelectric effect (emission of electrons when exposed to light) to a marked degree.

Sodium is by far the most commercially important alkali metal. Most processes for the production of sodium involve the electrolysis of molten sodium chloride. Inexpensive and available in tank-car quantities, the element is used to produce gasoline additives, polymers such as nylon and synthetic rubber, pharmaceuticals, and a number of metals such as tantalum, titanium, and silicon. It is also widely used as a heat exchanger and in sodium-vapour lamps. The yellow colour of the sodium-vapour lamp and the sodium flame (the basis of an analytical test for sodium) is identified with two prominent lines in the yellow portion of the light spectrum.

Significant uses

Two of the earliest uses of metallic sodium were in the manufacture of sodium cyanide and sodium peroxide. Significant quantities were used in the manufacture of tetraethyl lead as a gasoline additive, a market that disappeared with the advent of unleaded gasoline. Substantial amounts of sodium are used in the manufacture of sodium alkyl sulfates as the principal ingredient in synthetic detergents.

Sodium also is used as a starting material in the manufacture of sodium hydride (NaH) and sodium borohydride (NaBH4). In addition, sodium is employed in the production of dyes and dye intermediates, in the synthesis of perfumes, and in a wide variety of organic reductions. It is used in the purification of hydrocarbons and in the polymerization of unsaturated hydrocarbons. In many organic applications, sodium is used in the form of dispersions in hydrocarbon liquid media.

Molten sodium is an excellent heat-transfer fluid, and, because of this property, it has found use as coolant in liquid-metal fast breeder reactors. Sodium is used extensively in metallurgy as a deoxidant and as a reducing agent for the preparation of calcium, zirconium, titanium, and other transition metals. Commercial production of titanium involves reduction of titanium tetrachloride (TiCl4) with sodium. The products are metallic Ti and NaCl.

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#11 Re: Jai Ganesh's Puzzles » General Quiz » 2025-06-16 17:24:21

Hi,

#10419. What does the term in Physics/Chemisty Isotope mean?

#10420. What does the term in Physics/Chemistry Molecule mean?

#12 Re: Jai Ganesh's Puzzles » English language puzzles » 2025-06-16 17:09:19

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#5607. What does the verb (used without object) kindle mean?

#5608. What does the adjective kinetic mean?

#13 Re: Jai Ganesh's Puzzles » Doc, Doc! » 2025-06-16 16:32:15

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#2394. What does the medical term Photosensitive epilepsy mean?

#17 Science HQ » Lithium » 2025-06-15 16:46:16

Jai Ganesh
Replies: 0

Lithium

Gist

Lithium is a chemical element; it has symbol Li and atomic number 3. It is a soft, silvery-white alkali metal. Under standard conditions, it is the least dense metal and the least dense solid element.

Lithium is a type of medicine known as a mood stabiliser. It's used to treat mood disorders such as: mania (feeling highly excited, overactive or distracted) hypo-mania (similar to mania, but less severe)

Summary

Lithium is a chemical element; it has symbol Li and atomic number 3. It is a soft, silvery-white alkali metal. Under standard conditions, it is the least dense metal and the least dense solid element. Like all alkali metals, lithium is highly reactive and flammable, and must be stored in vacuum, inert atmosphere, or inert liquid such as purified kerosene or mineral oil. It exhibits a metallic luster. It corrodes quickly in air to a dull silvery gray, then black tarnish. It does not occur freely in nature, but occurs mainly as pegmatitic minerals, which were once the main source of lithium. Due to its solubility as an ion, it is present in ocean water and is commonly obtained from brines. Lithium metal is isolated electrolytically from a mixture of lithium chloride and potassium chloride.

The nucleus of the lithium atom verges on instability, since the two stable lithium isotopes found in nature have among the lowest binding energies per nucleon of all stable nuclides. Because of its relative nuclear instability, lithium is less common in the Solar System than 25 of the first 32 chemical elements even though its nuclei are very light: it is an exception to the trend that heavier nuclei are less common. For related reasons, lithium has important uses in nuclear physics. The transmutation of lithium atoms to helium in 1932 was the first fully human-made nuclear reaction, and lithium deuteride serves as a fusion fuel in staged thermonuclear weapons.

Lithium and its compounds have several industrial applications, including heat-resistant glass and ceramics, lithium grease lubricants, flux additives for iron, steel and aluminium production, lithium metal batteries, and lithium-ion batteries. These uses consume more than three-quarters of lithium production.

Lithium is present in biological systems in trace amounts. It has no established metabolic function in humans. Lithium-based drugs are useful as a mood stabilizer and antidepressant in the treatment of mental illness such as bipolar disorder.

Details

Lithium (Li) is a chemical element of Group 1 (Ia) in the periodic table, the alkali metal group, lightest of the solid elements. The metal itself—which is soft, white, and lustrous—and several of its alloys and compounds are produced on an industrial scale.

Element Properties

atomic number  :  3
atomic weight  :  6.941
melting point  :  180.5 °C (356.9 °F)
boiling point  :  1,342 °C (2,448 °F)
specific gravity  :  0.534 at 20 °C (68 °F)
oxidation state  :  +1

Occurrence and Production

Discovered in 1817 by Swedish chemist Johan August Arfwedson in the mineral petalite, lithium is also found in brine deposits and as salts in mineral springs; its concentration in seawater is 0.1 part per million (ppm). Lithium is also found in pegmatite ores, such as spodumene (LiAlSi2O6) and lepidolite (of varying structure), or in amblygonite (LiAlFPO4) ores, with Li2O contents ranging between 4 and 8.5 percent. It constitutes about 0.002 percent of Earth’s crust.

Until the 1990s the lithium chemical and metal market was dominated by American production from mineral deposits, but by the turn of the 21st century most production was derived from non-U.S. sources; Australia, Chile, and Portugal were the world’s largest suppliers. (Bolivia has half the world’s lithium deposits but is not a major producer of lithium.) The major commercial form is lithium carbonate, Li2CO3, produced from ores or brines by a number of different processes. Addition of hydrochloric acid (HCl) produces lithium chloride, which is the compound used to produce lithium metal by electrolysis. Lithium metal is produced by electrolysis of a fused mixture of lithium and potassium chlorides. The lower melting point of the mixture (400–420 °C, or 750–790 °F) compared with that of pure lithium chloride (610 °C, or 1,130 °F) permits lower-temperature operation of the electrolysis. Since the voltage at which decomposition of lithium chloride takes place is lower than that of potassium chloride, lithium is deposited at a purity level greater than 97 percent. Graphite anodes are used in the electrolytic production of lithium, while the cathodes are made of steel. The pure lithium formed at the cathode coalesces at the surface of the electrolyte to form a molten pool, which is protected from reaction with air by a thin film of the electrolyte. The lithium is ladled from the cell and cast by pouring it into a mold at a temperature only slightly above the melting point, leaving the solidified electrolyte behind. The solidified lithium is then remelted, and materials insoluble in the melt either float to the surface or sink to the bottom of the melt pot. The remelting step reduces the potassium content to less than 100 parts per million. Lithium metal, which can be drawn into wire and rolled into sheets, is softer than lead but harder than the other alkali metals and has the body-centred cubic crystal structure.

Many lithium alloys are produced directly by the electrolysis of molten salts, containing lithium chloride in the presence of a second chloride, or by the use of cathode materials that interact with the deposited lithium, introducing other elements into the melt.

Significant uses

The principal industrial applications for lithium metal are in metallurgy, where the active element is used as a scavenger (remover of impurities) in the refining of such metals as iron, nickel, copper, and zinc and their alloys. A large variety of nonmetallic elements are scavenged by lithium, including oxygen, hydrogen, nitrogen, carbon, sulfur, and the halogens. Lithium is utilized to a considerable extent in organic synthesis, both in laboratory reactions and industrially. A key reagent that is produced commercially on a large scale is n-butyllithium, C4H9Li. Its principal commercial use is as an initiator of polymerization, for example, in the production of synthetic rubber. It is also extensively used in the production of other organic chemicals, especially pharmaceuticals. Because of its light weight and large negative electrochemical potential, lithium metal, either pure or in the presence of other elements, serves as the anode (negative electrode) in many nonrechargeable lithium primary batteries. Since the early 1990s much work has been done on high-power rechargeable lithium storage batteries for electric vehicles and for power storage. The most successful of these provides for separation of the anode and a cathode such as LiCoO2 by a solvent-free conducting polymer that permits migration of the lithium cation, Li+. Smaller rechargeable lithium batteries are extensively used for cell phones, cameras, and other electronic devices.

Lightweight lithium-magnesium alloys and tough lithium-aluminum alloys, harder than aluminum alone, have structural applications in the aerospace and other industries. Metallic lithium is used in the preparation of compounds such as lithium hydride.

Additional Information

Lithium was discovered from a mineral, while other common alkali metals were discovered from plant material. This is thought to explain the origin of the element’s name; from ‘lithos’ (Greek for ‘stone’).

Appearance

A soft, silvery metal. It has the lowest density of all metals. It reacts vigorously with water.

Uses

The most important use of lithium is in rechargeable batteries for mobile phones, laptops, digital cameras and electric vehicles. Lithium is also used in some non-rechargeable batteries for things like heart pacemakers, toys and clocks.

Lithium metal is made into alloys with aluminium and magnesium, improving their strength and making them lighter. A magnesium-lithium alloy is used for armour plating. Aluminium-lithium alloys are used in aircraft, bicycle frames and high-speed trains.

Lithium oxide is used in special glasses and glass ceramics. Lithium chloride is one of the most hygroscopic materials known, and is used in air conditioning and industrial drying systems (as is lithium bromide). Lithium stearate is used as an all-purpose and high-temperature lubricant. Lithium carbonate is used in drugs to treat manic depression, although its action on the brain is still not fully understood. Lithium hydride is used as a means of storing hydrogen for use as a fuel.

Biological role

Lithium has no known biological role. It is toxic, except in very small doses.

Natural abundance

Lithium does not occur as the metal in nature, but is found combined in small amounts in nearly all igneous rocks and in the waters of many mineral springs. Spodumene, petalite, lepidolite, and amblygonite are the more important minerals containing lithium.

Most lithium is currently produced in Chile, from brines that yield lithium carbonate when treated with sodium carbonate. The metal is produced by the electrolysis of molten lithium chloride and potassium chloride

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#18 Re: Jai Ganesh's Puzzles » General Quiz » 2025-06-15 16:07:09

Hi,

#10417. What does the term in Chemistry Dry ice mean?

#10418. What does the term in Physics/Chemistry Ductility mean?

#19 Re: Jai Ganesh's Puzzles » English language puzzles » 2025-06-15 15:54:16

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#5605. What does the adjective grotesque mean?

#5606. What does the noun groundbreaking mean?

#20 Re: Jai Ganesh's Puzzles » Doc, Doc! » 2025-06-15 15:19:25

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#2393. What does the medical term Paraneoplastic syndrome mean?

#24 Science HQ » Radon » 2025-06-14 20:10:06

Jai Ganesh
Replies: 0

Radon

Gist

Radon is a naturally occurring radioactive gas, colorless and odorless, produced from the decay of uranium in rocks and soil. It can seep into buildings through cracks and openings, potentially leading to elevated indoor concentrations. While radon quickly dilutes outdoors, high indoor levels can pose a health risk, particularly lung cancer.

Radon is primarily used in scientific research and, historically, in some medical treatments. In scientific research, it's used as a tracer to monitor air masses and study atmospheric transport. It also plays a role in geological investigations and can be used as an indicator in earthquake forecasting. In the past, radon was used in some cancer treatments, but safer alternatives are now more common.

Summary

Radon is a naturally occurring radioactive gas that is colorless and odorless. Radon comes from the natural decay of uranium or thorium, elements found in rocks, soils, and water. Radon breaks down quickly, giving off radioactive particles. When inhaled, these radioactive particles can damage cells that line the lung.

Radon is a naturally occurring radioactive gas that is colorless and odorless. Radon comes from the natural decay of uranium or thorium, elements found in rocks, soils, and water. Radon breaks down quickly, giving off radioactive particles. When inhaled, these radioactive particles can damage cells that line the lung.

Radon gas is in nearly all outdoor air but usually at low levels. Radon is also found in water. A higher radon level in the water supply is more likely when the source is ground water, such as from a private well. Most public water supplies are sourced from surface water, such as lakes, rivers, and reservoirs.

Does radon affect health?

Scientists agree that radon causes lung cancer in humans. Being exposed to radon for a long period of time can lead to lung cancer. In the U.S., radon exposure is the second leading cause of lung cancer after cigarette smoking.

Exposure to the combination of radon gas and cigarette smoke creates an even greater chance of developing lung cancer. The majority of radon-related cancer deaths occur among smokers. However, it is estimated that about 10% of radon-related cancer deaths occur among nonsmokers.

Details

Radon is a chemical element; it has symbol Rn and atomic number 86. It is a radioactive noble gas and is colorless and odorless. Of the three naturally occurring radon isotopes, only 222Rn has a sufficiently long half-life (3.825 days) for it to be released from the soil and rock where it is generated. Radon isotopes are the immediate decay products of radium isotopes. The instability of 222Rn, its most stable isotope, makes radon one of the rarest elements. Radon will be present on Earth for several billion more years despite its short half-life, because it is constantly being produced as a step in the decay chains of 238U and 232Th, both of which are abundant radioactive nuclides with half-lives of at least several billion years. The decay of radon produces many other short-lived nuclides, known as "radon daughters", ending at stable isotopes of lead. 222Rn occurs in significant quantities as a step in the normal radioactive decay chain of 238U, also known as the uranium series, which slowly decays into a variety of radioactive nuclides and eventually decays into stable 206Pb. 220Rn occurs in minute quantities as an intermediate step in the decay chain of 232Th, also known as the thorium series, which eventually decays into stable 208Pb.

Radon was discovered in 1899 by Ernest Rutherford and Robert B. Owens at McGill University in Montreal, and was the fifth radioactive element to be discovered. First known as "emanation", the radioactive gas was identified during experiments with radium, thorium oxide, and actinium by Friedrich Ernst Dorn, Rutherford and Owens, and André-Louis Debierne, respectively, and each element's emanation was considered to be a separate substance: radon, thoron, and actinon. Sir William Ramsay and Robert Whytlaw-Gray considered that the radioactive emanations may contain a new element of the noble gas family, and isolated "radium emanation" in 1909 to determine its properties. In 1911, the element Ramsay and Whytlaw-Gray isolated was accepted by the International Commission for Atomic Weights, and in 1923, the International Committee for Chemical Elements and the International Union of Pure and Applied Chemistry (IUPAC) chose radon as the accepted name for the element's most stable isotope, 222Rn; thoron and actinon were also recognized by IUPAC as distinct isotopes of the element.

Under standard conditions, radon is gaseous and can be easily inhaled, posing a health hazard. However, the primary danger comes not from radon itself, but from its decay products, known as radon daughters. These decay products, often existing as single atoms or ions, can attach themselves to airborne dust particles. Although radon is a noble gas and does not adhere to lung tissue (meaning it is often exhaled before decaying), the radon daughters attached to dust are more likely to stick to the lungs. This increases the risk of harm, as the radon daughters can cause damage to lung tissue. Radon and its daughters are, taken together, often the single largest contributor to an individual's background radiation dose, but due to local differences in geology, the level of exposure to radon gas differs by location. A common source of environmental radon is uranium-containing minerals in the ground; it therefore accumulates in subterranean areas such as basements. Radon can also occur in ground water, such as spring waters and hot springs. Radon trapped in permafrost may be released by climate-change-induced thawing of permafrosts, and radon may also be released into groundwater and the atmosphere following seismic events leading to earthquakes, which has led to its investigation in the field of earthquake prediction. It is possible to test for radon in buildings, and to use techniques such as sub-slab depressurization for mitigation.

Epidemiological studies have shown a clear association between breathing high concentrations of radon and incidence of lung cancer. Radon is a contaminant that affects indoor air quality worldwide. According to the United States Environmental Protection Agency (EPA), radon is the second most frequent cause of lung cancer, after cigarette smoking, causing 21,000 lung cancer deaths per year in the United States. About 2,900 of these deaths occur among people who have never smoked. While radon is the second most frequent cause of lung cancer, it is the number one cause among non-smokers, according to EPA policy-oriented estimates. Significant uncertainties exist for the health effects of low-dose exposures.

Additional Information

Radon (Rn) is a chemical element, a heavy radioactive gas of Group 18 (noble gases) of the periodic table, generated by the radioactive decay of radium. (Radon was originally called radium emanation.) Radon is a colourless gas, 7.5 times heavier than air and more than 100 times heavier than hydrogen. The gas liquefies at −61.8 °C (−79.2 °F) and freezes at −71 °C (−96 °F). On further cooling, solid radon glows with a soft yellow light that becomes orange-red at the temperature of liquid air (−195 °C [−319 °F]).

Radon is rare in nature because its isotopes are all short-lived and because its source, radium, is a scarce element. The atmosphere contains traces of radon near the ground as a result of seepage from soil and rocks, both of which contain minute quantities of radium. (Radium occurs as a natural decay product of uranium present in various types of rocks.)

By the late 1980s, naturally occurring radon gas had come to be recognized as a potentially serious health hazard. Radioactive decay of uranium in minerals, especially granite, generates radon gas that can diffuse through soil and rock and enter buildings through basements (radon has a higher density than air) and through water supplies derived from wells (radon has a significant solubility in water). The gas can accumulate in the air of poorly ventilated houses. The decay of radon produces radioactive “daughters” (polonium, bismuth, and lead isotopes) that can be ingested from well water or can be absorbed in dust particles and then breathed into the lungs. Exposure to high concentrations of this radon and its daughters over the course of many years can greatly increase the risk of developing lung cancer. Indeed, radon is now thought to be the greatest cause of lung cancer among nonsmokers in the United States. Radon levels are highest in homes built over geological formations that contain uranium mineral deposits.

Concentrated samples of radon are prepared synthetically for medical and research purposes. Typically, a supply of radium is kept in a glass vessel in an aqueous solution or in the form of a porous solid from which the radon can readily flow. Every few days, the accumulated radon is pumped off, purified, and compressed into a small tube, which is then sealed and removed. The tube of gas is a source of penetrating gamma rays, which come mainly from one of radon’s decay products, bismuth-214. Such tubes of radon have been used for radiation therapy and radiography.

Natural radon consists of three isotopes, one from each of the three natural radioactive-disintegration series (the uranium, thorium, and actinium series). Discovered in 1900 by German chemist Friedrich E. Dorn, radon-222 (3.823-day half-life), the longest-lived isotope, arises in the uranium series. The name radon is sometimes reserved for this isotope to distinguish it from the other two natural isotopes, called thoron and actinon, because they originate in the thorium and the actinium series, respectively.

Radon-220 (thoron; 51.5-second half-life) was first observed in 1899 by American scientist Robert B. Owens and British scientist Ernest Rutherford, who noticed that some of the radioactivity of thorium compounds could be blown away by breezes in the laboratory. Radon-219 (actinon; 3.92-second half-life), which is associated with actinium, was found independently in 1904 by German chemist Friedrich O. Giesel and French physicist André-Louis Debierne. Radioactive isotopes having masses ranging from 204 through 224 have been identified, the longest-lived of these being radon-222, which has a half-life of 3.82 days. All the isotopes decay into stable end-products of helium and isotopes of heavy metals, usually lead.

Radon atoms possess a particularly stable electronic configuration of eight electrons in the outer shell, which accounts for the characteristic chemical inactivity of the element. Radon, however, is not chemically inert. For example, the existence of the compound radon difluoride, which is apparently more stable chemically than compounds of the other reactive noble gases, krypton and xenon, was established in 1962. Radon’s short lifetime and its high-energy radioactivity cause difficulties for the experimental investigation of radon compounds.

When a mixture of trace amounts of radon-222 and fluorine gas is heated to approximately 400 °C (752 °F), a nonvolatile radon fluoride is formed. The intense α-radiation of millicurie and curie amounts of radon provides sufficient energy to allow radon in such quantities to react spontaneously with gaseous fluorine at room temperature and with liquid fluorine at −196 °C (−321 °F).

Element Properties

atomic number  :  86
stablest isotope  :  (222)
melting point  :  −71 °C (−96 °F)
boiling point  :  −62 °C (−80 °F)
density (1 atm, 0 °C [32 °F])  :  9.73 g/litre (0.13 ounce/gallon)
oxidation states    :  0, +2.

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#25 Re: Jai Ganesh's Puzzles » General Quiz » 2025-06-14 19:25:05

Hi,

#10415. What does the term in Chemistry Chemical reaction mean?

#10416. What does the term in Chemistry Chemical compound mean?

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