sodium (Na) | chemical element | Britannica.com chemical element hydrogen (H) Sodium (Na), chemical element of Group 1 (Ia) of the periodic table (the alkali metal group). 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 the Earth’s crust. It occurs abundantly in nature in compounds , especially common salt —sodium chloride (NaCl)—which forms the mineral halite and comprises about 80 percent of the dissolved constituents of seawater. Properties and production Sodium is the most abundant of the alkali metals. Sodium chloride (table salt) is the most common compound of sodium, but many others also are known. Sir Humphry Davy first prepared sodium in its elemental form (1807) by the electrolysis of 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.

Because sodium is extremely reactive, it never occurs in the free state in the Earth’s crust. 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, 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 . alkali metal: Lighter than water, it 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, 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 neptunium (Np) 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. Principal compounds Sodium is highly reactive, forming a wide variety of compounds with nearly all inorganic and organic anions. It normally has an oxidation state of +1, and its single valence electron is lost with great ease, yielding the colourless sodium ion (Na+). Compounds that contain the sodium anion, Na-, have also been synthesized. The principal commercial sodium compounds are the chloride, carbonate , and sulfate . Britannica Stories Ringling Bros. Folds Its Tent The most important and familiar sodium compound is sodium chloride, or common salt, NaCl. Most other sodium compounds are prepared either directly or indirectly from sodium chloride, which occurs in seawater, in natural brines, and as rock salt.

Large quantities of sodium chloride are employed in the production of other heavy (industrial) chemicals as well as being used directly. During the period 2001–06, for example, American salt sales averaged about 28 million tons per year, of which about 16 million tons were used for ice and snow removal, 3.4 million tons for water conditioning, 1.6 million tons for food, and 2.2 million tons for the production of agricultural and industrial chemicals. Periodic Table of the Elements Other major commercial applications of sodium chloride include its use in the manufacture of chlorine and sodium hydroxide by electrolytic decomposition and in the production of sodium carbonate (Na2CO3) by the Solvay process. The electrolysis of aqueous sodium chloride produces sodium hypochlorite , NaOCl, a compound of sodium, oxygen , and chlorine used in large quantities in household chlorine bleach. Sodium hypochlorite is also utilized as an industrial bleach for paper pulp and textiles, for chlorination of water, and in certain medicinal preparations as an antiseptic and a fungicide. It is an unstable compound known only in aqueous solution. The carbonates contain the carbonate ion (CO32–).

Sodium bicarbonate , also called sodium hydrogen carbonate, or bicarbonate of soda, NaHCO3, is a source of carbon dioxide and so is used as an ingredient in baking powders, in effervescent salts and beverages, and as the main constituent of dry-chemical fire extinguishers. Its slight alkalinity makes it useful in treating gastric or urinary hyperacidity and acidosis. It is also employed in certain industrial processes, as in tanning and the preparation of wool. Sodium carbonate , or soda ash, Na2CO3, is widely distributed in nature, occurring as constituents of mineral waters and as the solid minerals natron, trona , and thermonatrite . Large quantities of this alkaline salt are used in making glass , detergents, and cleansers. Sodium carbonate is treated with carbon dioxide to produce sodium bicarbonate. The monohydrate form of sodium carbonate, Na2CO3·H2O, is employed extensively in photography as a constituent in developers.

Connect with Britannica Facebook Twitter YouTube Instagram Pinterest Sodium sulfate , Na2SO4, is a white crystalline solid or powder employed in the manufacture of kraft paper, paperboard, glass, and detergents and as a raw material for the production of various chemicals. It is obtained either from deposits of the sodium sulfate minerals mirabilite and thenardite or synthetically by the treatment of sodium chloride with sulfuric acid. The crystallized product is a hydrate, Na2SO4·10H2O, commonly known as Glauber’s salt. Sodium thiosulfate (sodium hyposulfite), Na2 S 2O3, is used by photographers to fix developed negatives and prints; it acts by dissolving the part of the silver salts coated onto film which remain unchanged by exposure to light. Sodium hydroxide (NaOH) is a corrosive, white crystalline solid that readily absorbs moisture until it dissolves. Commonly called caustic soda, or lye, sodium hydroxide is the most widely used industrial alkali. It is highly corrosive to animal and vegetable tissue.

The alkaline solutions it forms when dissolved in water neutralize acids in various commercial processes: in petroleum refining, it removes sulfuric and organic acids; in soapmaking, it reacts with fatty acids. Solutions of NaOH are used in the treatment of cellulose and in the manufacture of many chemicals. Sodium nitrate , or soda nitre, NaNO3, is commonly called Chile saltpetre , after its mineral deposits in northern Chile, the principal source. Sodium nitrate is used as a nitrogenous fertilizer and as a component of dynamite. Chemical properties Generally, elemental sodium is more reactive than lithium , and it reacts with water to form a strong base , NaOH. Its chemistry is well explored. Reaction with air, water, and hydrogen Sodium is ordinarily quite reactive with air, and the reactivity is a function of the relative humidity, or water-vapour content of the air. The corrosion of solid sodium by oxygen also is accelerated by the presence of small amounts of impurities in the sodium. In ordinary air, sodium metal reacts to form a sodium hydroxide film, which can rapidly absorb carbon dioxide from the air, forming sodium bicarbonate.

Sodium does not react with nitrogen , so sodium is usually kept immersed in a nitrogen atmosphere (or in inert liquids such as kerosene or naphtha). It is significantly more reactive in air as a liquid than as a solid, and the liquid can ignite at about 125 °C (257 °F). In a comparatively dry atmosphere, sodium burns quietly, giving off a dense white caustic smoke, which can cause choking and coughing. The temperature of burning sodium increases rapidly to more than 800 °C (1,500 °F), and under these conditions the fire is extremely difficult to extinguish. Special dry-powder fire extinguishers are required, since sodium reacts with carbon dioxide, a common propellant in regular fire extinguishers. Britannica Lists & Quizzes Eyjafjallajökull volcano Generally, alkali metals react with halogen gases, the degree of reactivity decreasing with increasing atomic weight of the halogen. Sodium is no exception to this statement. Under certain conditions of reaction, sodium and halogen vapours react to produce light (chemiluminescence).

Halogen acids, such as hydrochloric acid, react vigorously with sodium, yielding the sodium halides. The reactions are highly exothermic, with heats of reaction (energy given off) of −71.8 and −76.2 kcal, respectively, for the reactions with hydrofluoric and hydrochloric acids. Sodium is attacked by other strong mineral acids to form the corresponding salts. It reacts with the fumes of nitric acid at 15 °C (59 °F) to form sodium nitrate and with acetic and sulfuric acids to form sodium acetate and sodium sulfate. With molten sulfur it reacts violently to produce polysulfides; under more controlled conditions it reacts with organic solutions of sulfur. Liquid selenium and tellurium both react vigorously with solid sodium to form selenides and tellurides. Sodium shows relatively little reactivity with carbon, although lamellar (layerlike) materials can be prepared in which sodium is present between graphite layers. At 625 °C (1,157 °F) carbon monoxide reacts with sodium to form sodium carbide and sodium carbonate.

With the exception of the oxides of the Group 4 (IVb) metals (titanium, zirconium, and hafnium), the oxides of the transition metals are all reduced to the respective metals with elemental sodium. Sodium also reacts with a large number of metallic halides, displacing the metal from the salt and forming a sodium halide in the process. This reaction is used in the preparation of several of the transition metals themselves, including titanium and tantalum. Sodium and all the other alkali metals dissolve in liquid ammonia to give intense blue solutions, and at ordinary temperatures a slow reaction between sodium and ammonia occurs to form sodamide, NaNH2, and hydrogen, similar to the reaction of sodium with water to give NaOH and hydrogen. The reactions are Na + NH3 → NaNH2+ 1/2 H2 Na + H2O → NaOH + 1/2 H2 The reaction of alkali metal-ammonia solutions to form the amide and hydrogen can be catalyzed by the addition of many metals and metal oxides. Liquid ammonia is often used as a solvent for sodium, allowing a number of reactions to occur at ordinary temperatures that would otherwise need heat.

Sodium superoxide (NaO2), for example, can be formed by passing oxygen through ammonia solutions of sodium at −77 °C (−107 °F). Ammonia also serves as a solvent for reactions of sodium with arsenic , tellurium, antimony , bismuth , and a number of other low-melting metals. Sodium-ammonia solutions are used to blacken polytetrafluoroethylene (Teflon) to prepare its surface for cementing to other materials. The high reducing power of sodium-ammonia solutions makes them useful in a number of organic reactions known as Birch reductions. Organic reactions The organic reactions of sodium have been studied to a greater extent than those of any of the other alkali metals. Sodium reacts with anhydrous alcohols to form the respective alcoholates (or alkoxides) according to Na + ROH → RONa + 1/2 H2, in which R is the organic portion of the alcohol (R = CH3- for methanol, CH3CH2- for ethanol , etc.). The reaction is most vigorous with methanol and decreases with increasing molecular weight of the alcohol.

Sodium methoxide is produced on an industrial scale by reaction of sodium with excess methanol. Organic acids react with sodium to form sodium salts. The large negative free energy of formation of sodium halides permits the dehalogenation of a number of organic halides, the formation of the sodium halide being energetically favoured. The so-called Wurtz reaction—based on this principle—is used in organic synthesis to a considerable extent: 2RCl + 2Na → R−R +2NaCl. By this reaction, octane can be made from bromobutane and sodium. Organosodium compounds include a number in which the sodium atom is bonded directly to a carbon atom; an example is methylsodium, Na–CH3. Such compounds can be prepared by the action of sodium on mercury dialkyls or diaryls, as in the following equation: Hg(CH3)2 + 2Na → 2NaCH3 + Hg. Sodium reacts violently with a number of halogenated hydrocarbons. For example, a violent explosion occurs when a mixture of carbon tetrachloride and sodium is subjected to shock.

Even when the sodium is diluted to a considerable extent—as in sodium amalgam—a brisk reaction with carbon tetrachloride occurs. Reaction with metals Sodium is completely miscible with the alkali metals below it in the periodic table (potassium, rubidium , and cesium). A eutectic (that is, an alloy that melts lower than its components) melting at −10 °C (14 °F) is formed in the sodium-potassium system and is known commercially as NaK. Its composition is approximately 78 percent potassium, and it is used as a heat-transfer fluid and as an organic reactant. The eutectics formed in the sodium-rubidium and sodium-cesium binary systems melt, respectively, at −4.5 and −30 °C (24 and −22 °F). Sodium is the minor component with potassium and cesium of the ternary alloy NaKCs, melting at −78 °C (−108 °F). This fluid is the lowest-melting liquid alloy yet isolated. Sodium also forms alloys with the alkaline-earth metals.

Beryllium is soluble in sodium only to the extent of a few atomic percent at approximately 800 °C (1,500 °F). Liquid sodium and magnesium are only partially miscible. The degree of solubility in sodium of the alkaline-earth metals increases with increasing atomic weight, with the result that the solubility of calcium is 10 percent by weight at 700 °C (1,300 °F). In the sodium-strontium system, there is a considerable degree of miscibility. Sodium forms a number of compounds with barium , and several eutectics exist in the system. The precious metals, such as silver, gold , platinum , palladium , and iridium , and the white metals, such as lead , tin , bismuth, and antimony, alloy to an appreciable extent with liquid sodium. Cadmium and mercury also react with sodium, and a number of compounds exist in both binary systems. Seven sodium-mercury compounds, or amalgams, exist, with Hg2Na having the highest melting point (354 °C, or 669 °F).

Sodium amalgams are used chiefly for carrying out reactions in situations in which pure elemental sodium would be violently reactive and difficult to control. The solubility of transition metals in alkali metals is generally very low, often in the 1–10-parts per million range even at temperatures in excess of 500 °C (930 °F). Nuclear properties Natural sodium is the stable isotope of mass 23. Of the radioactive artificial isotopes, sodium-22 (2.6-year half-life, the longest half-life of a sodium isotope) is used as a radioactive tracer for natural sodium. Sodium-24 (15-hour half-life) is limited in use by its short life and is produced by irradiation in a nuclear reactor. Because of this reaction, a sodium-cooled reactor must have a second heat-transfer loop so that radioactive sodium does not come in contact with the environment . Other isotopes have half-lives of a minute or less. Biological properties Sodium salts, particularly sodium chloride, are found almost everywhere in biological material. Sodium is an essential element for life, as is potassium, and the two elements maintain a definite balance within the cell structure.

Electrolyte balance between the inside of the cell and the outside is maintained by “active transport” of potassium ions into the cell and sodium ions out of the cell. Most of the biological effects of sodium salts are the result of the cation (Na+), with the negative counter-ion apparently not playing a dominant role. The presence of salinity in soils is often detrimental to plant growth. Sodium ions replace calcium and other ions in clay complexes, transforming the clay to a sticky mass; water percolation is then drastically reduced, and the basicity of the soil rises markedly. The tolerance of fish to changes in salinity is often quite remarkable. Many marine bacteria and diatoms are able to tolerate salt concentrations as great as 25 percent. The minimum sodium requirement for mammals appears to be 0.05 percent of the diet, corresponding in a normal adult to a requirement of 1–2 grams (0.04–0.07 ounce) of salt per day, which results in an average sodium content of body tissues of 0.24 percent.

There is a wide variation of sodium content in the different tissues, with whole blood containing approximately 0.62 percent sodium chloride, whereas skin has a sodium content of less than 0.1 percent. There is a relationship between salt content and water balance of the body; a low salt intake causes loss of water. Considerable quantities of sodium are lost through the skin by perspiration, and considerable quantities can be excreted in the urine. Element Properties sodium - Student Encyclopedia (Ages 11 and up) Life could not exist without compounds of sodium. These compounds hold water in body tissues, and a severe deficiency of sodium can cause death. Blood contains sodium compounds in solution. Sodium compounds are used in industry in the manufacture of chemicals and pharmaceuticals, in metallurgy, in sodium vapor lamps, and in the production of hundreds of everyday products. One of the most common sodium compounds is table salt, or sodium chloride (NaCl). In its pure form sodium is a silver-white, soft and waxy metallic element. It is the sixth most abundant element on Earth and occurs in more than trace amounts in the stars and sun. Article History Compound vs Element - Difference and Comparison | Diffen Compound vs.

Element Diffen › Science › Chemistry Elements and compounds are pure chemical substances found in nature. The difference between an element and a compound is that an element is a substance made of same type of atoms, whereas a compound is made of different elements in definite proportions. Examples of elements include iron, copper, hydrogen and oxygen. Examples of compounds include water (H2O) and salt (Sodium Chloride - NaCl) Elements are listed according to their atomic number on the Periodic Table. Among the 117 known elements, 94 are naturally occurring like carbon, oxygen, hydrogen etc. 22 are artificially produced having undergone radioactive changes. The reason for this is their instability due to which they undergo radioactive decay over a period of time giving rise to new elements during the process like Uranium, Thorium, Bismuth etc. Elements combine in fixed ratios and give rise to stable compounds due to chemical bonds that facilitate compound formation. Comparison chart 4 References Differences in Properties Elements are distinguished by their name, symbol, atomic number, melting point, boiling point, density and ionization energies . In the Periodic Table, elements are arranged according to their atomic number and they are grouped according to similar chemical properties and are depicted by their symbols.

Atomic number – the atomic number is denoted by the letter Z and is the number of protons present in the nucleus of the atom of element. For e.g. carbon has 6 protons in its nucleus and for Carbon, Z = 6. Number of protons is also indicative of electric charge or number of electrons present in the nucleus which determines chemical properties of the element. Atomic Mass – the letter A indicates the atomic mass of the element which is the total number of protons and neutrons in the nucleus of an atom of the element. Isotopes of the same elements differ in their atomic masses. Isotopes – isotopes of an element have the same number of protons in their nucleus but differ in the number of neutrons. Naturally occurring elements have more than one stable isotope. Thus isotopes have similar chemical properties (due to same number of protons) but different nuclear properties (due to different number of neutrons). For e.g. carbon has three isotopes, Carbon - 12, Carbon -13 and Carbon - 14. Allotropes – atoms of an element can form bonds with each other in more than one way leading to difference in their chemical properties. For e.g.

carbon binds in a tetrahedron to form diamond and layers of hexagons of carbon forms graphite. Compounds are composed of different elements in a fixed proportion. For example, 1 atom of sodium (Na) combines with 1 atom of chlorine (Cl) to form one molecule of sodium chloride (NaCl) compound. The elements in a compound do not always retain their original properties and cannot be separated by physical means. The combining of elements is facilitated by their valency. Valency is defined as the number of hydrogen atoms required that can combine with an atom of the element forming the compound. Most compounds can exist as solids (low enough temperatures) and can be decomposed by the application of heat. Sometimes foreign elements are trapped inside crystal structure of compounds giving them a non homogeneous structure. Compounds are depicted by their chemical formula which follows the Hill system wherein carbon atoms are listed first, followed by hydrogen atoms after which elements are listed in alphabetical order. History of Elements and Compounds Elements were initially used as a reference to any state of matter like liquid, gas, air, solid etc. Indian, Japanese and Greek traditions refer to five elements namely, air, water, earth, fire and aether.

Aristotle conceptualized a new fifth element called 'quintessence' - which apparently formed the heavens. As research continued, many eminent scientists paved way for the current understanding and description of elements. Among them, work of Robert Boyle, Antoine Lavoisier, Dmitri Mendeleev are particularly notable. Lavoisier was the first to make a list of chemical elements and Mendeleev was the first to arrange elements according to their atomic number in the Periodic Table. The most current definition of an element is awarded by the studies carried out by Henry Moseley which states that the atomic number of an atom is expressed physically by its nuclear charge. Before the 1800s the usage of term compound could also mean a mixture. It was in the 19th century that meaning of a compound could be distinguished from a mixture. Alchemists like Joseph Louis Proust, Dalton and Berthollet and their studies on various compounds have given modern chemistry the current definition of compound. Proust’s work demonstrated to the world of chemistry that compounds were made constant composition of respective elements. CAS Number Every chemical substance is identified by its unique numerical identifier – the CAS (chemical abstracts service) number.

Hence every chemical compound and element has a CAS number. This makes database searches for elements and compounds more convenient. References a. a compound c. a homogeneous mixture b. an element d. - CHEMISTRY - 131 View Full Document This is the end of the preview. Sign up to access the rest of the document. Unformatted text preview: a. a compound c. a homogeneous mixture b. an element d. a heterogeneous mixture ANS: D PTS: 1 TOP: 2.2 - HOW DO WE CLASSIFY MATTER? 15. Zinc can be uniformly mixed in differing amounts in copper to an alloy called brass. Brass is an examples of which of the following? a. compounds c. homogeneous mixtures b. elements d. heterogeneous mixtures ANS: C PTS: 1 TOP: 2.2 - HOW DO WE CLASSIFY MATTER? 16. When a strong magnet is brought near to a sample which is known to contain both iron and sulfur the iron and the sulfur are separated from one another. What type of material is this sample? a. a compound b. a homogeneous mixture c. a heterogeneous mixture d. There is insufficient information to answer.

ANS: C PTS: 1 TOP: 2.2 - HOW DO WE CLASSIFY MATTER? 17. When a strong magnet is brought near to a sample which is known to contain both iron and sulfur the iron and the sulfur are not separated from one another. What type of material is this sample? a. a compound b. a homogeneous mixture c. a heterogeneous mixture d. There is insufficient information to answer. ANS: A PTS: 1 TOP: 2.2 - HOW DO WE CLASSIFY MATTER? 18. Sodium is a highly reactive metal and chlorine is a toxic gas, but when they come together the resulting material, sodium chloride, is essential for life. Which of the following is true when sodium and chlorine are brought into contact with one another? a. They form a heterogeneous mixture. c. They neutralize each other. b. They form a homogenous mixture. d. They form a compound. ANS: D PTS: 1 TOP: 2.2 - HOW DO WE CLASSIFY MATTER? 19. Aluminum and fluorine form a compound in which the aluminum to fluorine ratio is 1:3. What is the correct formula for this compound? a. AF 3 c.

AlF 3 b. AlFl 3 d. Al(F 2 ) 3 ANS: C PTS: 1 TOP: 2.2 - HOW DO WE CLASSIFY MATTER? 20. Sodium chlorate, an ingredient in many common herbicides, has sodium, chlorine and oxygen atoms in the ratio 1:1:3. What is the correct formula for sodium chlorate? a. NaCO 3 c. NaClO 3 b. SoClO 3 d. none of these ANS: C PTS: 1 TOP: 2.2 - HOW DO WE CLASSIFY MATTER? 21. Ammonium nitrate is a component of both fertilizers and explosives. Ammonium nitrate has nitrogen, hydrogen and oxygen atoms in the ratio 2:4:3. What is the correct formula for ammonium nitrate? a. N 4 H 8 O 6 c. N 1 H 2 O 1.5 b. N 2 H 4 O 3 d. all of these ANS: B PTS: 1 TOP: 2.2 - HOW DO WE CLASSIFY MATTER? 22.

Sodium bicarbonate has sodium, hydrogen, carbon and oxygen atoms in the ratio 1:1:1:3. What is the correct formula for sodium bicarbonate? a. NaBiCO 3 c. SoHCO 3 b. NaHCO 3 d. none of these ANS: B PTS: 1 TOP: 2.2 - HOW DO WE CLASSIFY MATTER? 23. Which of the following techniques would be most effective in separating the components of salt water?... CHAPTER 3 CHEMICAL BONDS MULTIPLE CHOICE 1. How many main types of chemical bonds exi CHAPTER 3 Sodium - Element information, properties and uses | Periodic Table Chemistry in its element: sodium (Promo) You're listening to Chemistry in its element brought to you by Chemistry World, the magazine of the Royal Society of Chemistry. (End promo) This week an essential element with a split personality. Here's David Read. David Read Sodium, like most elements in the periodic table could be said to have a dual personality.

On one side it is an essential nutrient for most living things, and yet, due to its reactive nature is also capable of wreaking havoc if you happen to combine it with something you shouldn't. As such sodium is found naturally only in compounds and never as the free element. Even so it is highly abundant, accounting for around 2.6 per cent of the earths crust by weight. Its most common compounds include dissolved sodium chloride (or table salt), its solid form, halite and as a charge balancing cation in zeolites. Aside from being an essential nutrient, the story of man and sodium is said to begin all the way back in the time of the Pharaohs in Ancient Egypt, with the first recorded mention of a sodium compound in the form of hieroglyphics. It is difficult to describe a pictogram through speech but imagine a squiggly line over the top of a hollow eye-shape, over the top of a semicircle, with a left-facing vulture image next to them all. This pictogram meant divine or pure and its name is the root of the word natron, which was used to refer to washing soda, or sodium carbonate decahydrate, as we would know it today.

Sodium carbonate was used in soap, and also, in the process of mummification thanks to its water absorbing and bacteria killing pH control properties. In medieval Europe, however, sodium carbonate was also used as a cure for headaches, and so took the name sodanum, from the Arabic suda, meaning headache. It was this terminology that inspired Sir Humphrey Davy to call the element sodium when he first isolated it by passing an electric current through caustic soda, or sodium hydroxide, in 1807. This process is known as electrolysis and using it Davy went on to isolate elemental potassium, calcium, magnesium and barium by a very similar method. Chemistry teachers often confuse children when they tell them about chemical symbols. Whilst ones like H, N, C and O all seem perfectly logical, abbreviating sodium to Na seems counterintuitive at first. However, if we consider the word natron, we can see where the abbreviated form came from. When isolated in metallic form, silvery white sodium is a violent element, immediately oxidising upon contact with air, and violently producing hydrogen gas which may burst into flame when brought into contact with water.

It is one of the highly reactive group one elements that are named the alkali metals. Like the other alkali metals, it has a very distinctive flame test - a bright orange colour, from the D-line emission. This is something you will have seen in all built up areas in the form of street lamps, which use sodium to produce the unnatural yellow light bathing our streets. This effect was first noted in 1860 by Kirchoff and Bunsen of Bunsen Burner fame. Almost all young chemists will have done a flame test at some point, and sodium chloride is a popular choice. Unfortunately, the intensity of the colour is such that if any of the compound is spilled into the Bunsen burner, it is cursed to burn with a blue and orange speckled flame seemingly forever. The reaction of sodium with water is a favourite demonstration, and clips of it abound on the internet. Sodium and its compounds have applications so diverse it would be impossible to mention them all here, a couple of examples include the fact that sodium is used to cool nuclear reactors, since it won't boil as water would at the high temperatures that are reached.

Sodium hydroxide can be used to remove sulfur from petrol and diesel, although the toxic soup of by-products that is formed has led to the process being outlawed in most countries. Sodium hydroxide is also used in biodiesel manufacture, and as a key component in products that remove blockages from drains. Baking soda actually contains sodium (it's in the name!) and its chemical name is sodium bicarbonate, where I'm sure you've come across it in baking or cooking where it undergoes thermal decomposition at above 70°C to release carbon dioxide - which then makes your dough rise. It is as an ion, however, that sodium really becomes important. An average human being has to take in around two grams of sodium a day - and virtually all of this will be taken in the form of salt in the diet. Sodium ions are used to build up electrical gradients in the firing of neurons in the brain. This involves sodium (and its big brother potassium) diffusing through cell membranes. Sodium diffuses in and is pumped back out, while potassium does the reverse journey. This can take up a huge amount of the body's energy - sometimes as much as 40 per cent.

I'd like to end with a brief story which highlights the dual personality of sodium. One man bought three and a half pounds of sodium metal from the internet and spent the evening reacting it with water in various shapes and sizes whilst he and his friends watched from a safe distance. The party was apparently a success, but he doesn't suggest hosting your own. The following day when the host came outside to check the area where he detonated the sodium was clear, he noticed that it was covered in swarms of yellow butterflies. After doing some research, he found that these butterflies had an interesting habit. The males search for sodium and gradually collect it, presenting it to their mates later as a ritual. So, that sums up the two faces of sodium. Its violent reactive nature contrasted with its use by amorous butterflies. Meera Senthilingam That was Southampton university's David Read with the two faced chemistry of sodium. Now next week, the chemical equivalent of train spotting. Brian Clegg It's easy to accuse the scientists who produce new, very heavy elements of being chemistry's train spotters.

Just as train spotters spend hours watching for a particular locomotive so they can underline it in their book, it may seem that these chemists laboriously produce an atom or two of a superheavy element as an exercise in ticking the box. But element 114 has provided more than one surprise, showing why such elements are well worth investigating. Meera Senthilingam And to find out why element 114 is worth the effort join Brian Clegg in next week's Chemistry in its element. (Promo) Chemistry in its element is brought to you by the Royal Society of Chemistry and produced by thenakedscientists.com . There's more information and other episodes of Chemistry in its element on our website at chemistryworld.org/elements . (End promo) Sodium, Chemical Element - reaction, water, uses, elements, examples, metal, gas, number PRONUNCIATION SO-dee-um Compounds of sodium have been known, of course, throughout human history. But sodium metal was not prepared until 1807. The reason is that sodium attaches itself very strongly to other elements. Its compounds are very difficult to break apart.

It was not until 1807 that English chemist Sir Humphry Davy (1778-1829) found a way to extract sodium from its compounds. (See sidebar on Davy in the calcium entry in Volume 1.) Sodium metal itself has relatively few uses. It reacts with other substances easily, sometimes explosively. However, many sodium compounds have many uses in industry, medicine, and everyday life. Discovery and naming Sodium carbonate, or soda (Na 2 CO 3 ), was probably the sodium compound best known to ancient peoples. It is the most common ore of sodium found in nature. This explains why glass was one of the first chemical products made by humans. Glass is made by heating sodium carbonate and calcium oxide (lime) together. When the mixture cools, it forms the hard, clear, transparent material called glass. Glass was being manufactured on a large scale in Egypt as early as 1370 B.C. The Egyptians called soda natron. Much later, the Romans used a similar name for the compound, natrium. These names explain the chemical symbol used for sodium, Na.

The name sodium probably originated from an Arabic word suda, meaning "headache." Soda was sometimes used as a cure for headaches among early peoples. The word suda also carried over into Latin to become sodanum, which also means "headache remedy." In the early 1800s, Davy found a way to extract a number of active elements from their compounds. Sodium was one of these elements. Davy's method involved melting a compound of the active element, then passing an electric current through the molten (melted) compound. Davy used sodium hydroxide (NaOH) to make sodium. Physical properties Sodium is a silvery-white metal with a waxy appearance. It is soft enough to be cut with a knife. The surface is bright and shiny when first cut, but quickly becomes dull as sodium reacts with oxygen in the air. A thin film of sodium oxide (Na 2 O) forms that hides the metal itself. Sodium's melting point is 97.82°C (208.1°F) and its boiling point is 881.4°C (1,618°F).

Its density is slightly less than that of water, 0.968 grams per cubic centimeter. Sodium is a good conductor of electricity. Chemical properties Sodium is a very active element. It combines with oxygen at room temperature. When heated, it combines very rapidly, burning with a brilliant golden-yellow flame. Sodium also reacts violently with water. (See accompanying sidebar.) It is so active that it is normally stored under a liquid with which it does not react. Kerosene or naphtha are liquids commonly used for this purpose. Sodium also reacts with most other elements and with many compounds. It reacts with acids to produce hydrogen gas. It also dissolves in mercury to form a sodium amalgam. An amalgam is an alloy of mercury and at least one other metal. Occurrence in nature Sodium never occurs as a free element in nature. It is much too active. It always occurs as part of a compound. The most common source of sodium in the Earth is halite. Halite is nearly pure sodium chloride (NaCl). It is also called rock salt. Halite can be found in underground deposits similar to coal mines. Those deposits were formed when ancient oceans evaporated (dried up), leaving sodium chloride behind.

Earth movements eventually buried those deposits. Now they can be mined to remove the sodium chloride. Sodium and water aren't friends O il and vinegar don't mix. But sodium and water really don't mix! Sodium reacts violently with water. The effect is fascinating. When sodium metal is first placed into water, it floats. But it immediately begins to react with water, releasing hydrogen gas: A great deal of energy is released in this reaction. It is enough to set fire to the hydrogen gas. The sodium metal reacts with water. So much heat is released that the sodium melts. It turns into a tiny ball of liquid sodium. At the same time, the sodium releases hydrogen from water. The hydrogen gas catches fire and causes the ball of sodium to go sizzling across the surface of the water. Sodium reacts violently with water. Sodium chloride can also be obtained from seawater and brine. Brine is similar to seawater, but it contains more dissolved salt. Removing sodium chloride from seawater or brine is easy. Sodium stored in oil to prevent its reaction with the surrounding air. All that is needed is to let the water evaporate. The sodium chloride is left behind.

It only needs to be separated from other chemicals that were also dissolved in the water. Isotopes There is only one naturally occurring isotope of sodium, sodium-23. Isotopes are two or more forms of an element. Isotopes differ from each other according to their mass number. The number written to the right of the element's name is the mass number. The mass number represents the number of protons plus neutrons in the nucleus of an atom of the element. The number of protons determines the element, but the number of neutrons in the atom of any one element can vary. Each variation is an isotope. Six radioactive isotopes of sodium are known also. A radioactive isotope is one that breaks apart and gives off some form of radiation. Radioactive isotopes are produced when very small particles are fired at atoms. These particles stick in the atoms and make them radioactive. Two radioactive isotopes of sodium—sodium-22 and sodium-24—are used in medicine and other applications. They can be used as tracers to follow sodium in a person's body. A tracer is a radioactive isotope whose presence in a system can easily be detected. The isotope is injected into the system at some point.

Inside the system, the isotope gives off radiation. That radiation can be followed by means of detectors placed around the system. Sodium-24 also has non-medical applications. For example, it is used to test for leaks in oil pipe lines. These pipe lines are usually buried underground. It may be difficult to tell when a pipe begins to leak. One way to locate a leak is to add some sodium-24 to the oil. If oil leaks out of the pipe, so does the sodium-24. The leaking oil may not be visible, but the leaking sodium-24 is easily detected. It is located by instruments that are designed to detect radiation. Extraction One way to obtain pure sodium metal is by passing an electric current through molten (melted) sodium chloride: This method is similar to the one used by Humphry Davy in 1808. But there is not much demand for sodium metal. Sodium compounds are much more common. A second and similar method is used to make a compound known as sodium hydroxide (NaOH). The sodium hydroxide is then used as a starting point for making other sodium compounds.

The method for making sodium hydroxide is called the chloralkali process. The name comes from the fact that both chlorine and an alkali metal (sodium) are produced at the same time. In this case, an electric current is passed through a solution of sodium chloride dissolved in water: Three useful products are obtained from this reaction: chlorine gas (Cl 2 ), hydrogen gas (H 2 ), and sodium hydroxide (NaOH). The chlor-alkali process is one of the most important industrial processes used today. Uses Sodium metal has a relatively small, but important, number of uses. For example, it is sometimes used as a heat exchange medium in nuclear power plants. A heat exchange medium is a material that picks up heat in one place and carries it to another place. Water is a common heat exchange medium. Some home furnaces burn oil or gas to heat water that travels through pipes and radiators in the house. The water gives off its heat through the radiators. Sodium does a similar job in nuclear power plants. Heat is produced by nuclear fission reactions at the core (center) of a nuclear reactor. In a nuclear fission reaction, large atoms break down to form smaller atoms.

As they do so, large amounts of heat energy are given off. Liquid sodium is sealed into pipes that surround the core of the reactor. As heat is generated, it is absorbed (taken up) by the sodium. The sodium is then forced through the pipes into a nearby room. In that room, the sodium pipes are wrapped around pipes filled with water. The heat in the sodium converts the water to steam. The steam is used to operate devices that generate electricity. Another use of sodium metal is in producing other metals. For example, sodium can be combined with titanium tetrachloride (TiCl 4 ) to make titanium metal: Sodium is also used to make artificial rubber. (Real rubber is made from the collected sap of rubber trees and is expensive.) The starting material for artificial rubber is usually a small molecule. The small molecule reacts with itself over and over again. It becomes a much larger molecule called a polymer. The polymer is the material that makes up the artificial rubber. Sodium metal is used as a catalyst in this reaction. A catalyst is a substance used to speed up or slow down a chemical reaction without undergoing any change itself. The combination of an electric current and sodium vapor produces a yellowish glow in street lamps.

Sodium is frequently used in making light bulbs. Sodium is first converted to a vapor (gas) and injected into a glass bulb. An electric current is passed through a wire or filament in the gas-filled bulb. The electric current causes the sodium vapor to give off a yellowish glow. Many street lamps today are sodium vapor lamps. Their advantage is that they do not produce as much glare as do ordinary lights. Compounds Almost all sodium compounds dissolve in water. When it rains, sodium compounds dissolve and are carried into the ground. Eventually, the compounds flow into rivers and then into the oceans. The ocean is salty partly because sodium compounds have been dissolved for many centuries. But that means that finding sodium compounds on land is somewhat unusual. They tend to be more common in desert areas because deserts experience low rainfall. So sodium compounds are less likely to be washed away. Huge beds of salt and sodium carbonate are sometimes found in desert areas. Dozens of sodium compounds are used today in all fields. Some of the most important of these compounds are discussed below. Sodium chloride (NaCl). The most familiar use of sodium chloride is as a flavor enhancer in food. It is best known as table salt.

Large amounts of sodium chloride are also added to prepared foods, such as canned, bottled, frozen, and dried foods. One purpose of adding sodium chloride to these foods is to improve their flavors. But another purpose is to prevent them from decaying. Sodium chloride kills bacteria in foods. It has been used for hundreds of years as a food preservative. The "pickling" or "salting" of a food, for example, means the adding of salt to that food to keep it from spoiling. This process is one reason people eat so much salt in their foods today. Most people eat a lot of prepared foods. Those prepared foods contain a lot of salt. People are often not aware of all the salt they take in when they eat such foods. Sodium chloride is also the starting point for making other sodium compounds. In fact, this application is probably the number one use for sodium chloride. Almost all sodium compounds dissolve in water. They tend to be more common in desert areas because deserts experience low rainfall. Sodium carbonate (Na2CO3). Sodium carbonate is also known by other names, such as soda, soda ash, sal soda, and washing soda. It is also used as the starting point in making other sodium compounds.

A growing use is in water purification Sodium chloride (table salt) crystals. and sewage treatment systems. The sodium carbonate is mixed with other chemicals that react to form a thick, gooey solid. The solid sinks to the bottom of a tank, carrying impurities present in water or waste water. Sodium carbonate is also used to make a very large number of commercial products, such as glass, pulp and paper, soaps and detergents, and textiles. Sodium bicarbonate (NaHCO3). When sodium bicarbonate is dissolved in water, it produces a fizzing reaction. That reaction can be used in many household situations. For example, the fizzy gas can help bread batter rise. The "rising" of the batter is caused by bubbles released when sodium bicarbonate (baking soda) is added to milk in the batter. Certain kinds of medications, such as Alka-Seltzer, also include sodium bicarbonate. The fizzing is one of the effects of taking Alka-Seltzer that helps settle the stomach. Sodium bicarbonate is also used in mouthwashes, cleaning solutions, wool and silk cleaning systems, fire extinguishers, and mold preventatives in the timber industry.

Examples of lesser known compounds are as follows: sodium alginate (NaC 6 H 7 O 6 ): a thickening agent in ice cream and other prepared foods; manufacture of cement; coatings for paper products; water-based paints sodium bifluoride (KHF 2 ): preservative for animal specimens; antiseptic (germ-killer); etching of glass; manufacture of tin plate sodium diuranate, or "uranium yellow" (Na 2 U 2 O 7 ): used to produce yellowish-orange glazes for ceramics sodium fluorosilicate (Na 2 SiF 6 ): used to make "fluoride" toothpastes that protect against cavities; insecticides and rodenticides (rat-killers); moth repellent; wood and leather preservative; manufacture of laundry soaps and "pearl-like" enamels sodium metaborate (NaBO 2 ): herbicide sodium paraperiodate (Na 3 H 2 IO 6 ): helps tobacco to bum more completely and cleanly; helps paper products retain strength when wet sodium stearate (NaOOCC 17 H 35 ): keeps plastics from breaking down; waterproofing agent; additive in toothpastes

 and cosmetics sodium zirconium glycolate (NaZrH 3 (H 2 COCOO) 3 ): deodorant; germicide (germ-killer); fire-retardant A common compound of sodium, sodium bicarbonate, produces a fizzing reaction.

It is an ingredient in such medications as Alka-Seltzer. Health effects Sodium has a number of important functions in plants, humans, and animals. In humans, for example, sodium is involved in controlling the amount of fluid present in cells. An excess or lack of sodium can cause cells to gain or lose water. Either of these changes can prevent cells from carrying out their normal functions. Dietary concerns P eople sometimes talk about the amount of "sodium" in their diet. Or they may refer to the amount of "salt" in their diet. The two terms are similar, but not exactly alike. In the body, sodium occurs most often as sodium chloride. A common name for sodium chloride is salt. The Committee on Dietary Allowance of the U.S. Food and Nutrition Board recommends that a person take in about 1,100 to 3,300 milligrams of sodium per day. The human body actually needs only about 500 milligrams of sodium. Studies show that the average American takes in about 2,300 to 6,900 milligrams of sodium per day. This high level of sodium intake troubles many health experts.

Too much sodium can affect the body's ability to digest fats, for example. The most serious problem, however, may be hypertension. Hypertension is another name for "high blood pressure." A person with high blood pressure may be at risk for stroke, heart attack, or other serious health problems. Sodium is also involved in sending nerve messages to and from cells. These impulses control the way muscles move. Again, an excess or lack of sodium can result in abnormal nerve and muscle behavior. Sodium is also needed to control the digestion of foods in the stomach and intestines. Also read article about Sodium from Wikipedia User Contributions: The Chemistry of Carbon The Chemistry of Carbon Inorganic Carbon For more than 200 years, chemists have divided compounds into two categories. Those that were isolated from plants or animals were called organic, while those extracted from ores and minerals were inorganic. Organic chemistry is often defined as the chemistry of carbon. But this definition would include calcium carbonate (CaCO3) and graphite, which more closely resemble inorganic compounds.

We will therefore define organic chemistry as the study of compounds, such as formic acid (HCO2H), methane (CH4), and vitamin C (C6H8O6), that contain both carbon and hydrogen. The chemistry of carbon is dominated by three factors. 1. Carbon forms unusually strong C-C single bonds, C=C double bonds, and carbon-carbon triple bonds. 2. The electronegativity of carbon (EN = 2.55) is too small to allow carbon to form C4- ions with most metals and too large for carbon to form C4+ ions when it reacts with nonmetals. Carbon therefore forms covalent bonds with many other elements. 3. Carbon forms strong double and triple bonds with a number of other nonmetals, including N, O, P, and S. Carbon occurs as a variety of allotropes. There are two crystalline forms diamond and graphite and a number of amorphous (noncrystalline) forms, such as charcoal, coke, and carbon black. References to the characteristic hardness of diamond (from the Greek adamas, "invincible") date back at least 2600 years.

It was not until 1797, however, that Smithson Tennant was able to show that diamonds consist solely of carbon. The properties of diamond are remarkable. It is among the least volatile substances known (MP = 3550oC, BP = 4827oC), it is also the hardest substance known, and it expands less on heating than any other material. The properties of diamond are a logical consequence of its structure. Carbon, with four valence electrons, forms covalent bonds to four neighboring carbon atoms arranged toward the corners of a tetrahedron, as shown in the figure below. Each of these sp3-hybridized atoms is then bound to four other carbon atoms, which form bonds to four other carbon atoms, and so on. As a result, a perfect diamond can be thought of as a single giant molecule. The strength of the individual C-C bonds and their arrangement in space give rise to the unusual properties of diamond. In some ways, the properties of graphite are like those of diamond. Both compounds boil at 4827oC, for example. But graphite is also very different from diamond.

Diamond (3.514 g/cm3) is much denser than graphite (2.26 g/cm3). Whereas diamond is the hardest substance known, graphite is one of the softest. Diamond is an excellent insulator, with little or no tendency to carry an electric current. Graphite is such a good conductor of electricity that graphite electrodes are used in electrical cells. The physical properties of graphite can be understood from the structure of the solid shown in the figure below. Graphite consists of extended planes of sp2-hybridized carbon atoms in which each carbon is tightly bound to three other carbon atoms. (The strong bonds between carbon atoms within each plane explain the exceptionally high melting point and boiling point of graphite.) The distance between these planes of atoms, however, is very much larger than the distance between the atoms within the planes. Because the bonds between planes are weak, it is easy to deform the solid by allowing one plane of atoms to move relative to another. As a result, graphite is soft enough to be used in pencils and as a lubricant in motor oil. "Lead" pencils do not, incidentally, contain lead.

(This is fortunate because many people chew pencils and lead compounds are toxic.) Lead pencils contain graphite, or "black lead" as it was once known, which is mixed with clay (20% to 60% by weight) and then baked to form a ceramic rod. Increasing the percentage of clay makes the pencil harder, so that less graphite is deposited on the paper. The characteristic properties of graphite and diamond might lead you to expect that diamond would be more stable than graphite. This is not what is observed experimentally. The standard enthalpy of formation of diamond ( Hof = 2.425 kJ/mol) is slightly larger than the enthalpy of formation of graphite, which is the most stable form of carbon at 25oC and 1 atm pressure. At very high temperatures and pressures, diamond becomes more stable than graphite. In 1955 General Electric developed a process to make industrial-grade diamonds by treating graphite with a metal catalyst at temperatures of 2000 to 3000 K and pressures above 125,000 atm. Roughly 40% of industrial-quality diamonds are now synthetic. Although gem-quality diamonds can be synthesized, the costs involved are prohibitive.

Both diamond and graphite occur as regularly packed crystals. Other forms of carbon are amorphous they lack a regular structure. Charcoal, carbon black, and coke are all amorphous forms of carbon. Charcoal results from heating wood in the absence of oxygen. To make carbon black, natural gas or other carbon compounds are burned in a limited amount of air to give a thick, black smoke that contains extremely small particles of carbon, which can be collected when the gas is cooled and passed through an electrostatic precipitator. Coke is a more regularly structured material, closer in structure to graphite than either charcoal or carbon black, which is made from coal. Carbides: Covalent, Ionic, and Interstitial Although carbon is essentially inert at room temperature, it reacts with less electronegative negative elements at high temperatures to form compounds known as carbides. When carbon reacts with an element of similar size and electronegativity, a covalent carbide is produced. Silicon carbide, for example, is made by treating silicon dioxide from quartz with an excess of carbon in an electric furnace at 2300 K.

SiO2(s) + 2 OH- At one time, miners' lamps were fueled by the combustion of acetylene prepared from the reaction of calcium carbide with water. Interstitial carbides, such as tungsten carbide (WC), form when carbon combines with a metal that has an intermediate electronegativity and a relatively large atomic radius. In these compounds, the carbon atoms pack in the holes (interstices) between planes of metal atoms. The interstitial carbides, which include TiC, ZrC, and MoC retain the properties of metals. They act as alloys, rather than as either salts or covalent compounds. Although the different forms of carbon are essentially inert at room temperature, they combine with oxygen at high temperatures to produce a mixture of carbon monoxide and carbon dioxide. 2 C(s) + H2(g) Because this mixture of gases is formed by the reaction of charcoal or coke with water it is often referred to as water gas. It is also known as town gas because it was once made by towns and cities for use as a fuel. Water gas, or town gas, was a common fuel for both home and industrial use before natural gas became readily available.

The H2 burns to form water, and the CO is oxidized to CO2. Eventually, as our supply of natural gas is depleted, it will become economical to replace natural gas with other fuels, such as water gas, that can be produced from our abundant supply of coal. CO and CO2 are both colorless gases. CO boils at -191.5oC, and CO2 sublimes at -78.5oC. Although CO has no odor or taste, CO2 has a faint, pungent odor and a distinctly acidic taste. Both are dangerous substances but at very different levels of exposure. Air contaminated with as little as 0.002 grams of CO per liter can be fatal because CO binds tightly to the hemoglobin and myoglobin that carry oxygen through the blood. CO2 is not lethal until the concentration in the air approaches 15%. At that point, it has replaced so much oxygen that a person who attempts to breathe this atmosphere suffocates. The danger of CO2 poisoning is magnified by the fact that CO2 is roughly 1.5 times more dense than the air in our atmosphere. Thus, CO2 can accumulate at the bottom of tanks or wells.

CO2 In the Atmosphere CO2 influences the temperature of the atmosphere through the greenhouse effect, which works as follows. CO2 absorbs some of the lower energy, longer wavelength infrared radiation from the sun that would otherwise be reflected back from the surface of the planet. Thus, CO2 in the atmosphere traps heat. Although there are other factors at work, it is worth noting that Venus, whose atmosphere contains a great deal of CO2, has a surface temperature of roughly 400oC, whereas Mars, with little or no atmosphere, has a surface temperature of -50oC. There are many sources of CO2 in the atmosphere. Over geologic time scales, the largest source has been volcanoes. Within the last century, the combustion of petroleum, coal, and natural gas has made a significant contribution to atmospheric levels of CO2 (see figure below). Between 1958 and 1978, the average level of CO2 in the atmosphere increased by 6%, from 315.8 to 334.6 ppm.

At one time, the amount of CO2 released to the atmosphere was not a matter for concern because natural processes that removed CO2 from the atmosphere could compensate for the CO2 that entered the atmosphere. The vast majority of the CO2 liberated by volcanic action, for example, was captured by calcium oxide or magnesium oxide to form calcium carbonate or magnesium carbonate. CaO(s) It then reacts with water to form carbonic acid, H2CO3. CO2(aq) H2O(l) H2CO3(aq) As a result of these reactions, the sea contains about 60 times more CO2 than the atmosphere. Can the sea absorb more CO2 from the atmosphere, or is it near its level of saturation? Is the rate at which the sea absorbs CO2 greater than the rate at which we are adding it to the atmosphere? The observed increase in the concentration of CO2 in recent years suggests pessimistic answers to these two questions. A gradual warming of the earth's atmosphere could result from continued increases in CO2 levels, with adverse effects on the climate and therefore the agriculture of at least the northern hemisphere. The Chemistry of Carbonates: CO32- and HCO3- Egg shells are almost pure calcium carbonate.

CaCO3 can also be found in the shells of many marine organisms and in both limestone and marble. The fact that none of these substances dissolve in water suggests that CaCO3 is normally insoluble in water. Calcium carbonate will dissolve in water saturated with CO2, however, because carbonated water (or carbonic acid) reacts with calcium carbonate to form calcium bicarbonate, which is soluble in water. CaCO3(s) + 2 HCO3-(aq) When water rich in carbon dioxide flows through limestone formations, part of the limestone dissolves. If the CO2 escapes from this water, or if some of the water evaporates, solid CaCO3 is redeposited. When this happens as water runs across the roof of a cavern, stalactites, which hang from the roof of the cave, are formed. If the water drops before the carbonate reprecipitates, stalagmites, which grow from the floor of the cave, are formed. The chemistry of carbon dioxide dissolved in water is the basis of the soft drink industry. The first artificially carbonated beverages were introduced in Europe at the end of the nineteenth century.

Carbonated soft drinks today consist of carbonated water, a sweetening agent (such as sugar, saccharin, or aspartame), an acid to impart a sour or tart taste, flavoring agents, coloring agents, and preservatives. As much as 3.5 liters of gaseous CO2 dissolve in a liter of soft drink. The CO2 contributes the characteristic bite associated with carbonated beverages. Carbonate chemistry plays an important role in other parts of the food industry as well. Baking soda, or bicarbonate of soda, is sodium bicarbonate, NaHCO3, a weak base, which is added to recipes to neutralize the acidity of other ingredients. Baking powder is a mixture of baking soda and a weak acid, such as tartaric acid or calcium hydrogen phosphate (CaHPO4). When mixed with water, the acid reacts with the HCO3- ion to form CO2 gas, which causes the dough or batter to rise. HCO3-(aq) + CO2(g) Before commercial baking powders were available, cooks obtained the same effect by mixing roughly a teaspoon of baking soda with a cup of sour milk or buttermilk.

The acids that give sour milk and buttermilk their characteristic taste also react with the bicarbonate ion to give CO2. Fullerenes In 1985 Richard Smalley and co-workers at Rice University made a uniquely stable form of carbon by vaporizing graphite with a laser. The apparatus in which this experiment was performed was designed to create small molecules that were clusters of atoms. In this cluster generator, a pulse of helium gas was swept over the surface of the graphite as it was excited with the laser. The mixture of helium and carbon atoms that vaporized from the graphite surface cooled as the gas expanded, and molecules with the formula C60 were formed that have a structure that has the symmetry of a soccer-ball. Because this structure resembles the geodesic dome invented by R. Buckminster Fuller, C60 was named buckminsterfullerene, or "buckyball" for short.

Although it was formally a new form of pure carbon, C60 seemed to be nothing more than a laboratory curiosity until 1990, when Wolfgang Kratschmer and Konsantinos Kostiropoulos, at the Max Planck Institute in Heidelberg, reported that this material could be made by heating a graphite rod in an atmosphere of helium until the graphite evaporated. Once it was known that C60 could be synthesized in large quantities, researchers looked for, and found it, in such common sources as the flame of a sooty candle. It has even been found in the black soot that collects on the glass screen in front of a fireplace. Some of the excitement chemists experienced when C60 was synthesized can be understood by contrasting this form of pure carbon with diamond and graphite. C60 is unique because it exists as distinct molecules, not extended arrays of atoms. Equally important, C60 can be obtained as a pure substance, whereas the surfaces of diamond and graphite are inevitably contaminated by hydrogen atoms that bind to the carbon atoms on the surface. C60 is now known to be a member of a family of compounds known as the fullerenes.

Other compounds in this family include C32, C44, C50, C58, and C70. C60 may be the most important of the fullerenes because it is the most perfectly symmetric molecule possible, spinning in the solid at a rate of more than 100 million times per second. Because of their symmetry, C60 molecules pack as regularly as Ping-Pong balls. The resulting solid has unusual properties. Initially, it is as soft as graphite, but when compressed by 30%, it becomes harder than diamond. When this pressure is released, the solid springs back to its original volume. C60 therefore has the remarkable property that it bounces back when shot at a metal surface at high speeds. C60 also has the remarkable ability to form compounds in which it is an insulator, a conductor, a semiconductor, or a superconductor. By itself, C60 is a semiconductor. When mixed with just enough potassium to give a compound with the empirical formula K3C60, it conducts electricity like a metal. When excess potassium is added, this solid becomes an insulator.

When K3C60 is cooled to 18 K, the result is a superconductor. The potential of fullerene chemistry for both practical materials and laboratory curiosities is large enough to explain why this molecule can be described as "exocharmic" it exudes charm.

Question: Sodium bicarbonate consists of sodium, carbon, oxygen and which other element?
Answer: HYDROGEN