Sodium compounds

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Sodium atoms have 11 electrons, one more than the stable configuration of the noble gas neon. As a result, sodium usually forms ionic compounds involving the Na+ cation. [1] Sodium is a reactive alkali metal and is much more stable in ionic compounds. It can also form intermetallic compounds and organosodium compounds. Sodium compounds are often soluble in water.

Contents

Metallic sodium

Metallic sodium is generally less reactive than potassium and more reactive than lithium. [2] Sodium metal is highly reducing, with the standard reduction potential for the Na+/Na couple being −2.71 volts, [3] though potassium and lithium have even more negative potentials. [4] The thermal, fluidic, chemical, and nuclear properties of molten sodium metal have caused it to be one of the main coolants of choice for the fast breeder reactor. Such nuclear reactors are seen as a crucial step for the production of clean energy. [5]

Salts and oxides

The structure of sodium chloride, showing octahedral coordination around Na and Cl centres. This framework disintegrates when dissolved in water and reassembles when the water evaporates. NaCl polyhedra.png
The structure of sodium chloride, showing octahedral coordination around Na and Cl centres. This framework disintegrates when dissolved in water and reassembles when the water evaporates.

Sodium compounds are of immense commercial importance, being particularly central to industries producing glass, paper, soap, and textiles. [6] The most important sodium compounds are table salt (NaCl), soda ash (Na2 CO3), baking soda (NaHCO3), caustic soda (NaOH), sodium nitrate (NaNO3), di- and tri-sodium phosphates, sodium thiosulfate (Na2 S2O3·5H2O), and borax (Na2 B 4O7·10H2O). [7] In compounds, sodium is usually ionically bonded to water and anions and is viewed as a hard Lewis acid. [8]

Two equivalent images of the chemical structure of sodium stearate, a typical soap. Sodium stearate v2.svg
Two equivalent images of the chemical structure of sodium stearate, a typical soap.

Most soaps are sodium salts of fatty acids. Sodium soaps have a higher melting temperature (and seem "harder") than potassium soaps. [7] Sodium containing mixed oxides are promising catalysts [9] and photocatalysts. [10] Photochemically intercalated sodium ion enhances the photoelectrocatalytic activity of WO3. [11]

Like all the alkali metals, sodium reacts exothermically with water. The reaction produces caustic soda (sodium hydroxide) and flammable hydrogen gas. When burned in air, it forms primarily sodium peroxide with some sodium oxide. [12]

Aqueous solutions

Sodium tends to form water-soluble compounds, such as halides, sulfates, nitrates, carboxylates and carbonates. The main aqueous species are the aquo complexes [Na(H2O)n]+, where n = 4–8; with n = 6 indicated from X-ray diffraction data and computer simulations. [13]

Direct precipitation of sodium salts from aqueous solutions is rare because sodium salts typically have a high affinity for water. An exception is sodium bismuthate (NaBiO3). [14] Because of the high solubility of its compounds, sodium salts are usually isolated as solids by evaporation or by precipitation with an organic antisolvent, such as ethanol; for example, only 0.35 g/L of sodium chloride will dissolve in ethanol. [15] Crown ethers, like 15-crown-5, may be used as a phase-transfer catalyst. [16]

Sodium content of samples is determined by atomic absorption spectrophotometry or by potentiometry using ion-selective electrodes. [17]

Electrides and sodides

Like the other alkali metals, sodium dissolves in ammonia and some amines to give deeply colored solutions; evaporation of these solutions leaves a shiny film of metallic sodium. The solutions contain the coordination complex (Na(NH3)6)+, with the positive charge counterbalanced by electrons as anions; cryptands permit the isolation of these complexes as crystalline solids. Sodium forms complexes with crown ethers, cryptands and other ligands. [18]

For example, 15-crown-5 has a high affinity for sodium because the cavity size of 15-crown-5 is 1.7–2.2 Å, which is enough to fit the sodium ion (1.9 Å). [19] [20] Cryptands, like crown ethers and other ionophores, also have a high affinity for the sodium ion; derivatives of the alkalide Na− are obtainable [21] by the addition of cryptands to solutions of sodium in ammonia via disproportionation. [22]

Organosodium compounds

The structure of the complex of sodium (Na , shown in yellow) and the antibiotic monensin-A. Monensin2.png
The structure of the complex of sodium (Na , shown in yellow) and the antibiotic monensin-A.

Many organosodium compounds have been prepared. Because of the high polarity of the C-Na bonds, they behave like sources of carbanions (salts with organic anions). Some well-known derivatives include sodium cyclopentadienide (NaC5H5) and trityl sodium ((C6H5)3CNa). [23] Sodium naphthalene, Na+[C10H8•]−, a strong reducing agent, forms upon mixing Na and naphthalene in ethereal solutions. [24]

Intermetallic compounds

Sodium forms alloys with many metals, such as potassium, calcium, lead, and the group 11 and 12 elements. Sodium and potassium form KNa2 and NaK. NaK is 40–90% potassium and it is liquid at ambient temperature. It is an excellent thermal and electrical conductor. Sodium-calcium alloys are by-products of the electrolytic production of sodium from a binary salt mixture of NaCl-CaCl2 and ternary mixture NaCl-CaCl2-BaCl2. Calcium is only partially miscible with sodium, and the 1-2% of it dissolved in the sodium obtained from said mixtures can be precipitated by cooling to 120 °C and filtering. [25]

In a liquid state, sodium is completely miscible with lead. There are several methods to make sodium-lead alloys. One is to melt them together and another is to deposit sodium electrolytically on molten lead cathodes. NaPb3, NaPb, Na9Pb4, Na5Pb2, and Na15Pb4 are some of the known sodium-lead alloys. Sodium also forms alloys with gold (NaAu2) and silver (NaAg2). Group 12 metals (zinc, cadmium and mercury) are known to make alloys with sodium. NaZn13 and NaCd2 are alloys of zinc and cadmium. Sodium and mercury form NaHg, NaHg4, NaHg2, Na3Hg2, and Na3Hg. [26]

See also

Related Research Articles

<span class="mw-page-title-main">Alkali metal</span> Group of highly reactive chemical elements

The alkali metals consist of the chemical elements lithium (Li), sodium (Na), potassium (K), rubidium (Rb), caesium (Cs), and francium (Fr). Together with hydrogen they constitute group 1, which lies in the s-block of the periodic table. All alkali metals have their outermost electron in an s-orbital: this shared electron configuration results in their having very similar characteristic properties. Indeed, the alkali metals provide the best example of group trends in properties in the periodic table, with elements exhibiting well-characterised homologous behaviour. This family of elements is also known as the lithium family after its leading element.

<span class="mw-page-title-main">Hydroxide</span> Chemical compound

Hydroxide is a diatomic anion with chemical formula OH−. It consists of an oxygen and hydrogen atom held together by a single covalent bond, and carries a negative electric charge. It is an important but usually minor constituent of water. It functions as a base, a ligand, a nucleophile, and a catalyst. The hydroxide ion forms salts, some of which dissociate in aqueous solution, liberating solvated hydroxide ions. Sodium hydroxide is a multi-million-ton per annum commodity chemical. The corresponding electrically neutral compound HO• is the hydroxyl radical. The corresponding covalently bound group –OH of atoms is the hydroxy group. Both the hydroxide ion and hydroxy group are nucleophiles and can act as catalysts in organic chemistry.

<span class="mw-page-title-main">Potassium</span> Chemical element, symbol K and atomic number 19

Potassium is the chemical element with the symbol K 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. 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, and occurs in many minerals such as orthoclase, a common constituent of granites and other igneous rocks.

<span class="mw-page-title-main">Sodium</span> Chemical element, symbol Na and atomic number 11

Sodium is a chemical element with the symbol Na 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.

In chemistry, a salt is a chemical compound consisting of an ionic assembly of positively charged cations and negatively charged anions, which results in a compound with no net electric charge. A common example is table salt, with positively charged sodium ions and negatively charged chloride ions.

The term chloride refers either to a chloride ion, which is a negatively charged chlorine atom, or a non-charged chlorine atom covalently bonded to the rest of the molecule by a single bond. Many inorganic chlorides are salts. Many organic compounds are chlorides. The pronunciation of the word "chloride" is.

<span class="mw-page-title-main">Ammonium</span> Polyatomic ion (NH₄, charge +1)

The ammonium cation is a positively charged polyatomic ion with the chemical formula NH+4 or [NH4]+. It is formed by the protonation of ammonia. Ammonium is also a general name for positively charged (protonated) substituted amines and quaternary ammonium cations, where one or more hydrogen atoms are replaced by organic or other groups.

The chlorite ion, or chlorine dioxide anion, is the halite with the chemical formula of ClO−
2. A chlorite (compound) is a compound that contains this group, with chlorine in the oxidation state of +3. Chlorites are also known as salts of chlorous acid.

<span class="mw-page-title-main">Chromate and dichromate</span> Chromium(VI) anions

Chromate salts contain the chromate anion, CrO2−
4. Dichromate salts contain the dichromate anion, Cr
2O2−
7. They are oxyanions of chromium in the +6 oxidation state and are moderately strong oxidizing agents. In an aqueous solution, chromate and dichromate ions can be interconvertible.

In chemistry, perxenates are salts of the yellow xenon-containing anion XeO4−
6. This anion has octahedral molecular geometry, as determined by Raman spectroscopy, having O–Xe–O bond angles varying between 87° and 93°. The Xe–O bond length was determined by X-ray crystallography to be 1.875 Å.

Classical qualitative inorganic analysis is a method of analytical chemistry which seeks to find the elemental composition of inorganic compounds. It is mainly focused on detecting ions in an aqueous solution, therefore materials in other forms may need to be brought to this state before using standard methods. The solution is then treated with various reagents to test for reactions characteristic of certain ions, which may cause color change, precipitation and other visible changes.

<span class="mw-page-title-main">Cryptand</span> Cyclic, multidentate ligands adept at encapsulating cations

In chemistry, cryptands are a family of synthetic, bicyclic and polycyclic, multidentate ligands for a variety of cations. The Nobel Prize for Chemistry in 1987 was given to Donald J. Cram, Jean-Marie Lehn, and Charles J. Pedersen for their efforts in discovering and determining uses of cryptands and crown ethers, thus launching the now flourishing field of supramolecular chemistry. The term cryptand implies that this ligand binds substrates in a crypt, interring the guest as in a burial. These molecules are three-dimensional analogues of crown ethers but are more selective and strong as complexes for the guest ions. The resulting complexes are lipophilic.

<span class="mw-page-title-main">Radical anion</span> Free radical species

In organic chemistry, a radical anion is a free radical species that carries a negative charge. Radical anions are encountered in organic chemistry as reduced derivatives of polycyclic aromatic compounds, e.g. sodium naphthenide. An example of a non-carbon radical anion is the superoxide anion, formed by transfer of one electron to an oxygen molecule. Radical anions are typically indicated by .

<span class="mw-page-title-main">Ozonide</span> Polyatomic ion (O3, charge –1), or cyclic compounds made from ozone and alkenes

Ozonide is the polyatomic anion O−3. Cyclic organic compounds formed by the addition of ozone to an alkene are also called ozonides.

<span class="mw-page-title-main">Electride</span> Ionic compound with electrons as the anion

An electride is an ionic compound in which an electron is the anion. Solutions of alkali metals in ammonia are electride salts. In the case of sodium, these blue solutions consist of [Na(NH3)6]+ and solvated electrons:

A solvated electron is a free electron in a solution, and is the smallest possible anion. Solvated electrons occur widely. Often, discussions of solvated electrons focus on their solutions in ammonia, which are stable for days, but solvated electrons also occur in water and other solvents – in fact, in any solvent that mediates outer-sphere electron transfer. The solvated electron is responsible for a great deal of radiation chemistry.

<span class="mw-page-title-main">Gold compounds</span>

Gold compounds are compounds by the element gold (Au). Although gold is the most noble of the noble metals, it still forms many diverse compounds. The oxidation state of gold in its compounds ranges from −1 to +5, but Au(I) and Au(III) dominate its chemistry. Au(I), referred to as the aurous ion, is the most common oxidation state with soft ligands such as thioethers, thiolates, and organophosphines. Au(I) compounds are typically linear. A good example is Au(CN)−2, which is the soluble form of gold encountered in mining. The binary gold halides, such as AuCl, form zigzag polymeric chains, again featuring linear coordination at Au. Most drugs based on gold are Au(I) derivatives.

An alkalide is a chemical compound in which alkali metal atoms are anions with a charge or oxidation state of −1. Until the first discovery of alkalides in the 1970s, alkali metals were known to appear in salts only as cations with a charge or oxidation state of +1. These types of compounds are of theoretical interest due to their unusual stoichiometry and low ionization potentials. Alkalide compounds are chemically related to the electrides, salts in which trapped electrons are effectively the anions.

<span class="mw-page-title-main">Lead compounds</span> Type of compound

Compounds of lead exist with lead in two main oxidation states: +2 and +4. The former is more common. Inorganic lead(IV) compounds are typically strong oxidants or exist only in highly acidic solutions.

<span class="mw-page-title-main">Astatine compounds</span>

Astatine compounds are compounds that contain the element astatine (At). As this element is very radioactive, few compounds have been studied. Less reactive than iodine, astatine is the least reactive of the halogens. Its compounds have been synthesized in nano-scale amounts and studied as intensively as possible before their radioactive disintegration. The reactions involved have been typically tested with dilute solutions of astatine mixed with larger amounts of iodine. Acting as a carrier, the iodine ensures there is sufficient material for laboratory techniques to work. Like iodine, astatine has been shown to adopt odd-numbered oxidation states ranging from −1 to +7.

References

  1. ↑ Lawrie Ryan; Roger Norris (31 July 2014). Cambridge International AS and A Level Chemistry Coursebook (illustrated ed.). Cambridge University Press, 2014. p. 36. ISBN   978-1-107-63845-7.
  2. ↑ De Leon, N. "Reactivity of Alkali Metals". Indiana University Northwest. Archived from the original on 16 October 2018. Retrieved 7 December 2007.
  3. ↑ Atkins, Peter W.; de Paula, Julio (2002). Physical Chemistry (7th ed.). W. H. Freeman. ISBN   978-0-7167-3539-7. OCLC   3345182.
  4. ↑ Davies, Julian A. (1996). Synthetic Coordination Chemistry: Principles and Practice. World Scientific. p. 293. ISBN   978-981-02-2084-6. OCLC   717012347.
  5. ↑ "Fast Neutron Reactors | FBR - World Nuclear Association". World-nuclear.org. Retrieved 2022-10-04.
  6. ↑ Alfred Klemm, Gabriele Hartmann, Ludwig Lange, "Sodium and Sodium Alloys" in Ullmann's Encyclopedia of Industrial Chemistry 2005, Wiley-VCH, Weinheim. doi : 10.1002/14356007.a24_277
  7. 1 2 Holleman, Arnold F.; Wiberg, Egon; Wiberg, Nils (1985). Lehrbuch der Anorganischen Chemie (in German) (91–100 ed.). Walter de Gruyter. pp. 931–943. ISBN   978-3-11-007511-3.
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  9. ↑ Kim, Heeyeon; Lee, Suhyeong; Jang, Seoyoung; Yu, Ji-haeng; Yoo, Jong Suk; Oh, Jangwon (5 September 2021). "Effect of facile nitrogen doping on catalytic performance of NaW/Mn/SiO2 for oxidative coupling of methane". Applied Catalysis B: Environmental. 292: 120161. doi: 10.1016/j.apcatb.2021.120161 . ISSN   0926-3373.
  10. ↑ Praxedes, Fabiano R.; Nobre, Marcos A. L.; Poon, Po S.; Matos, Juan; Lanfredi, Silvania (5 December 2021). "Nanostructured KxNa1-xNbO3 hollow spheres as potential materials for the photocatalytic treatment of polluted water". Applied Catalysis B: Environmental. 298: 120502. doi:10.1016/j.apcatb.2021.120502. ISSN   0926-3373. Archived from the original on 8 January 2022. Retrieved 8 January 2022.
  11. ↑ Szkoda, M.; Trzciński, K.; Trykowski, G.; Łapiński, M.; Lisowska-Oleksiak, A. (5 December 2021). "Influence of alkali metal cations on the photoactivity of crystalline and exfoliated amorphous WO3 – photointercalation phenomenon". Applied Catalysis B: Environmental. 298: 120527. doi: 10.1016/j.apcatb.2021.120527 . ISSN   0926-3373.
  12. ↑ Greenwood and Earnshaw, p. 84
  13. ↑ Lincoln, S. F.; Richens, D. T.; Sykes, A. G. (2004). "Metal Aqua Ions". Comprehensive Coordination Chemistry II. p. 515. doi:10.1016/B0-08-043748-6/01055-0. ISBN   978-0-08-043748-4.
  14. ↑ Dean, John Aurie; Lange, Norbert Adolph (1998). Lange's Handbook of Chemistry. McGraw-Hill. ISBN   978-0-07-016384-3.
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  16. ↑ Starks, Charles M.; Liotta, Charles L.; Halpern, Marc (1994). Phase-Transfer Catalysis: Fundamentals, Applications, and Industrial Perspectives. Chapman & Hall. p. 162. ISBN   978-0-412-04071-9. OCLC   28027599.
  17. ↑ Levy, G. B. (1981). "Determination of Sodium with Ion-Selective Electrodes". Clinical Chemistry. 27 (8): 1435–1438. doi:10.1093/clinchem/27.8.1435. PMID   7273405. Archived from the original on 5 February 2016. Retrieved 26 November 2011.
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  22. ↑ Holleman, A. F.; Wiberg, E.; Wiberg, N. (2001). Inorganic Chemistry. Academic Press. ISBN   978-0-12-352651-9. OCLC   48056955.
  23. ↑ Renfrow, W. B. Jr.; Hauser, C. R. (1943). "Triphenylmethylsodium". Organic Syntheses .; Collective Volume, vol. 2, p. 607
  24. ↑ Greenwood and Earnshaw, p. 111
  25. ↑ Paul Ashworth; Janet Chetland (31 December 1991). Brian, Pearson (ed.). Speciality chemicals: Innovations in industrial synthesis and applications (illustrated ed.). London: Elsevier Applied Science. pp. 259–278. ISBN   978-1-85166-646-1. Archived from the original on 16 December 2021. Retrieved 27 July 2021.
  26. ↑ Habashi, Fathi (21 November 2008). Alloys: Preparation, Properties, Applications. John Wiley & Sons, 2008. pp. 278–280. ISBN   978-3-527-61192-8.
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