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Sodium is a
chemical element In chemistry, an element is a pure Chemical substance, substance consisting only of atoms that all have the same numbers of protons in their atomic nucleus, nuclei. Unlike chemical compounds, chemical elements cannot be broken down into simp ...
with the
symbol A symbol is a mark, sign, or that indicates, signifies, or is understood as representing an , , or . Symbols allow people to go beyond what is n or seen by creating linkages between otherwise very different s and s. All (and ) is achieved th ...
 Na (from Latin ''natrium'') and
atomic number 300px, The Rutherford–Bohr model of the hydrogen atom () or a hydrogen-like ion (). In this model it is an essential feature that the photon energy (or frequency) of the electromagnetic radiation emitted (shown) when an electron jumps from one ...
 11. It is a soft, silvery-white, highly reactive
metal A metal (from Greek Greek may refer to: Greece Anything of, from, or related to Greece Greece ( el, Ελλάδα, , ), officially the Hellenic Republic, is a country located in Southeast Europe. Its population is approximately 10.7 mi ...

metal
. Sodium is an
alkali metal The alkali metals consist of the chemical element Image:Simple Periodic Table Chart-blocks.svg, 400px, Periodic table, The periodic table of the chemical elements In chemistry, an element is a pure substance consisting only of atoms that ...
, being in
group 1Group 1 may refer to: * Alkali metal, a chemical element classification for Alkali metal * Group 1 (racing), a historic (until 1981) classification for Touring car racing, applied to standard touring cars. Comparable to modern FIA Group N * Group One ...
of the periodic table. Its only stable
isotope Isotopes are two or more types of atoms that have the same atomic number (number of protons A proton is a subatomic particle, symbol or , with a positive electric charge Electric charge is the physical property of matter that causes it ...
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 In geology Geology (from the Ancient Greek γῆ, ''gē'' ("earth") and -λoγία, ''-logia'', ("study of", "discourse")) is an Earth science concerned with the solid Earth, the rock (geology), rocks of which it is composed, and the proces ...

minerals
such as
feldspar Feldspars are a group of rock-forming aluminium tectosilicate minerals, containing sodium, calcium, potassium or barium. The most common members of the feldspar group are the ''plagioclase'' (sodium-calcium) feldspars and the ''alkali'' (potas ...
s,
sodalite Sodalite ( ) is a royal blue Royal blue is both a bright shade and a dark shade of azure blue Blue is one of the three primary color, primary colours of pigments in painting and traditional colour theory, as well as in the RGB color ...

sodalite
, and
rock salt Halite ( or ), commonly known as rock salt, is a type of salt Salt is a mineral composed primarily of sodium chloride (NaCl), a chemical compound belonging to the larger class of Salt (chemistry), salts; salt in its natural form as a cry ...

rock salt
(NaCl). Many salts of sodium are highly water-soluble: sodium ions have been leached by the action of water from the
Earth's
Earth's
mineral In geology and mineralogy, a mineral or mineral species is, broadly speaking, a solid chemical compound with a fairly well-defined chemical composition and a specific crystal structure that occurs naturally in pure form.John P. Rafferty, ed. (2 ...

mineral
s over eons, and thus sodium and
chlorine Chlorine is a chemical element with the Symbol (chemistry), symbol Cl and atomic number 17. The second-lightest of the halogens, it appears between fluorine and bromine in the periodic table and its properties are mostly intermediate betw ...

chlorine
are the most common dissolved elements by weight in the oceans. Sodium was first isolated by
Humphry Davy Sir Humphry Davy, 1st Baronet (17 December 177829 May 1829) was a Cornish people, Cornish chemist and inventor who invented the Davy lamp and a very early form of arc lamp. He is also remembered for isolating, by using electricity, a series of ...

Humphry Davy
in 1807 by the
electrolysis In chemistry Chemistry is the science, scientific study of the properties and behavior of matter. It is a natural science that covers the Chemical element, elements that make up matter to the chemical compound, compounds composed of atoms ...

electrolysis
of
sodium hydroxide Sodium hydroxide, also known as lye A lye is a metal hydroxide traditionally obtained by leaching wood ashes, or a strong alkali In chemistry Chemistry is the scientific discipline involved with Chemical element, elements and chem ...

sodium hydroxide
. Among many other useful sodium compounds,
sodium hydroxide Sodium hydroxide, also known as lye A lye is a metal hydroxide traditionally obtained by leaching wood ashes, or a strong alkali In chemistry Chemistry is the scientific discipline involved with Chemical element, elements and chem ...

sodium hydroxide
(
lye A lye is a metal hydroxideMetal hydroxides are hydroxides of metals. They are often strong base (chemistry), bases. They consist of hydroxide anions and metallic cations. Some metal hydroxides, such as alkali metal hydroxides, ionize completel ...
) is used in
soap manufacture
soap manufacture
, and
sodium chloride Sodium chloride , commonly known as salt (although sea salt also contains other chemical salt (chemistry), salts), is an ionic compound with the chemical formula NaCl, representing a 1:1 ratio of sodium and chloride ions. With Molar mass, molar ...
(
edible salt Salt is a mineral In geology and mineralogy, a mineral or mineral species is, broadly speaking, a solid chemical compound with a fairly well-defined chemical composition and a specific crystal structure that occurs naturally in pure form ...
) is a
de-icing De-icing is the process of removing snow Snow comprises individual ice crystals that grow while suspended in the atmosphere—usually within clouds—and then fall, accumulating on the ground where they undergo further changes. It cons ...
agent and a nutrient for animals including humans. Sodium is an
essential element In the context of nutrition, a mineral is a chemical element Image:Simple Periodic Table Chart-blocks.svg, 400px, Periodic table, The periodic table of the chemical elements In chemistry, an element is a pure substance consisting only of atoms ...
for all animals and some plants. Sodium ions are the major cation in the
extracellular fluid In cell biology Cell biology (also cellular biology or cytology) is a branch of biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, ...
(ECF) and as such are the major contributor to the ECF
osmotic pressure
osmotic pressure
and ECF compartment volume. Loss of water from the ECF compartment increases the sodium concentration, a condition called
hypernatremia Hypernatremia, also spelled hypernatraemia, is a high concentration of sodium in the Serum (blood), blood. Early symptoms may include a strong feeling of thirst, weakness, nausea, and anorexia (symptom), loss of appetite. Severe symptoms include de ...
.
Isotonic
Isotonic
loss of water and sodium from the ECF compartment decreases the size of that compartment in a condition called ECF
hypovolemia Hypovolemia, also known as volume depletion or volume contraction, is a state of abnormally low extracellular fluid in the body. This may be due to either a loss of both salt and water or a decrease in blood volume. Hypovolemia refers to the loss ...
. By means of the
sodium-potassium pump Na⁺/K⁺-ATPase (sodium Sodium is a chemical element Image:Simple Periodic Table Chart-blocks.svg, 400px, Periodic table, The periodic table of the chemical elements In chemistry, an element is a pure substance consisting only of at ...
, living human cells pump three sodium ions out of the cell in exchange for two potassium ions pumped in; comparing ion concentrations across the cell membrane, inside to outside,
potassium Potassium is a chemical element upright=1.0, 500px, The chemical elements ordered by link=Periodic table In chemistry Chemistry is the science, scientific study of the properties and behavior of matter. It is a natural science ...

potassium
measures about 40:1, and sodium, about 1:10. In
nerve cells
nerve cells
, the electrical charge across the cell membrane enables transmission of the nerve impulse—an
action potential In physiology Physiology (; ) is the scientific Science (from the Latin Latin (, or , ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally spoken in the are ...

action potential
—when the charge is dissipated; sodium plays a key role in that activity.


Characteristics


Physical

Sodium at
standard temperature and pressure Standard temperature and pressure (STP) are standard Standard may refer to: Flags * Colours, standards and guidons * Standard (flag), a type of flag used for personal identification Norm, convention or requirement * Standard (metrology), a ...
is a soft silvery metal that combines with oxygen in the air and forms grayish white
sodium oxide Sodium oxide is a chemical compound A chemical compound is a chemical substance composed of many identical molecules (or molecular entity, molecular entities) composed of atoms from more than one chemical element, element held together by chemi ...
unless immersed in oil or inert gas, which are the conditions it is usually stored in. Sodium metal can be easily cut with a knife and is a good conductor of electricity and heat because it has only one electron in its valence shell, resulting in weak
metallic bonding Metallic bonding is a type of chemical bond A chemical bond is a lasting attraction between atoms, ions or molecules that enables the formation of chemical compounds. The bond may result from the Coulomb's law, electrostatic force of att ...

metallic bonding
and free electrons, which carry energy. Due to having low atomic mass and large atomic radius, sodium is third-least dense of all elemental metals and is one of only three metals that can float on water, the other two being lithium and potassium.Greenwood and Earnshaw, p. 75 The melting (98 °C) and boiling (883 °C) points of sodium are lower than those of lithium but higher than those of the heavier alkali metals potassium, rubidium, and caesium, following periodic trends down the group. These properties change dramatically at elevated pressures: at 1.5
Mbar The bar is a metric unit of pressure, but not part of the International System of Units International is an adjective (also used as a noun) meaning "between nations". International may also refer to: Music Albums * International (Kevin Michae ...
, the color changes from silvery metallic to black; at 1.9 Mbar the material becomes transparent with a red color; and at 3 Mbar, sodium is a clear and transparent solid. All of these high-pressure
allotrope Allotropy or allotropism () is the property of some chemical element Image:Simple Periodic Table Chart-blocks.svg, 400px, Periodic table, The periodic table of the chemical elements In chemistry, an element is a pure substance consisting o ...
s are insulators and
electride Cavities and channels in an electride An electride is an ionic compound structure of sodium chloride Sodium chloride , commonly known as salt (although sea salt also contains other chemical salt (chemistry), salts), is an ionic compound with ...
s. In a
flame test A flame test is an analytical procedure used in chemistry Chemistry is the scientific discipline involved with Chemical element, elements and chemical compound, compounds composed of atoms, molecules and ions: their composition, structure ...

flame test
, sodium and its compounds glow yellow because the excited 3s electrons of sodium emit a
photon The photon ( el, φῶς, phōs, light) is a type of elementary particle In , an elementary particle or fundamental particle is a that is not composed of other particles. Particles currently thought to be elementary include the fundamental s ...

photon
when they fall from 3p to 3s; the wavelength of this photon corresponds to the D line at about 589.3 nm. Spin-orbit interactions involving the electron in the 3p orbital split the D line into two, at 589.0 and 589.6 nm;
hyperfine structure In atomic physics, hyperfine structure is defined by small shifts in otherwise degenerate energy levels and the resulting splittings in those energy levels of atom An atom is the smallest unit of ordinary matter In classical physics an ...
s involving both orbitals cause many more lines.


Isotopes

Twenty isotopes of sodium are known, but only 23Na is stable. 23Na is created in the
carbon-burning process The carbon-burning process or carbon fusion is a set of nuclear fusion 400 px, The nuclear binding energy curve. The formation of nuclei with masses up to iron-56 releases energy, as illustrated above. Nuclear fusion is the process by which tw ...
in stars by fusing two
carbon Carbon (from la, carbo "coal") is a with the C and 6. It is lic and —making four s available to form s. It belongs to group 14 of the periodic table. Carbon makes up only about 0.025 percent of Earth's crust. Three occur naturally, ...

carbon
atoms together; this requires temperatures above 600 megakelvins and a star of at least three solar masses. Two
radioactive Radioactive decay (also known as nuclear decay, radioactivity, radioactive disintegration or nuclear disintegration) is the process by which an unstable atomic nucleus The atomic nucleus is the small, dense region consisting of s and s ...

radioactive
,
cosmogenic Cosmogenic nuclides (or cosmogenic isotopes) are rare nuclide A nuclide (or nucleide, from nucleus, also known as nuclear species) is a class of atoms characterized by their number of proton A proton is a subatomic particle, symbol or , with a ...
isotopes are the byproduct of
cosmic ray spallation Cosmic ray spallation, also known as the x-process, is a set of naturally occurring nuclear reactions causing nucleosynthesis Nucleosynthesis is the process that creates new atomic nuclei The atomic nucleus is the small, dense region consistin ...
: 22Na has a
half-life Half-life (symbol ''t''1⁄2) is the time required for a quantity to reduce to half of its initial value. The term is commonly used in nuclear physics Nuclear physics is the field of physics Physics is the natural science that studies ...
of 2.6 years and 24Na, a half-life of 15 hours; all other isotopes have a half-life of less than one minute. Two
nuclear isomer A nuclear isomer is a metastable In chemistry Chemistry is the science, scientific study of the properties and behavior of matter. It is a natural science that covers the Chemical element, elements that make up matter to the chemical c ...
s have been discovered, the longer-lived one being 24mNa with a half-life of around 20.2 milliseconds. Acute neutron radiation, as from a nuclear
criticality accident A criticality accident is an uncontrolled nuclear fission chain reaction. It is sometimes referred to as a critical excursion, critical power excursion, or divergent chain reaction. Any such event involves the unintended accumulation or arrangeme ...
, converts some of the stable 23Na in human blood to 24Na; the neutron radiation dosage of a victim can be calculated by measuring the concentration of 24Na relative to 23Na.


Chemistry

Sodium atoms have 11 electrons, one more than the stable configuration of the
noble gas The noble gases (historically also the inert gases; sometimes referred to as aerogens) make up a class of chemical element In chemistry Chemistry is the study of the properties and behavior of . It is a that covers the that m ...
neon Neon is a chemical element In chemistry Chemistry is the study of the properties and behavior of . It is a that covers the that make up matter to the composed of s, s and s: their composition, structure, properties, behavior ...

neon
. The first and second
ionization energies
ionization energies
are 495.8 kJ/mol and 4562 kJ/mol, respectively. As a result, sodium usually forms
ionic compound In chemistry Chemistry is the study of the properties and behavior of . It is a that covers the that make up matter to the composed of s, s and s: their composition, structure, properties, behavior and the changes they undergo during ...
s involving the Na+ cation. Metallic sodium is generally less reactive than
potassium Potassium is a chemical element upright=1.0, 500px, The chemical elements ordered by link=Periodic table In chemistry Chemistry is the science, scientific study of the properties and behavior of matter. It is a natural science ...

potassium
and more reactive than
lithium Lithium (from el, λίθος, lithos, lit=stone) is a chemical element In chemistry Chemistry is the study of the properties and behavior of . It is a that covers the that make up matter to the composed of s, s and s: the ...

lithium
. Sodium metal is highly reducing, with the
standard reduction potential Redox potential (also known as oxidation / reduction potential, ''ORP'', ''pe'', ''E_'', or E_) is a measure of the tendency of a chemical species A chemical species is a chemical substance A chemical substance is a form of matter In clas ...
for the Na+/Na couple being −2.71 volts, though potassium and lithium have even more negative potentials.


Salts and oxides

Sodium compounds are of immense commercial importance, being particularly central to industries producing
glass Glass is a non- crystalline, often transparency and translucency, transparent amorphous solid, that has widespread practical, technological, and decorative use in, for example, window panes, tableware, and optics. Glass is most often formed by ...

glass
,
paper Paper is a thin sheet material Material is a substance Substance may refer to: * Substance (Jainism), a term in Jain ontology to denote the base or owner of attributes * Chemical substance, a material with a definite chemical composition ...

paper
,
soap Soap is a salt (chemistry), salt of a fatty acid used in a variety of cleansing and lubricating products. In a domestic setting, soaps are surfactants usually used for washing, bathing, and other types of housekeeping. In industrial settings, ...

soap
, and
textile A textile is a flexible material made by creating an interlocking bundle of yarn Yarn is a long continuous length of interlocked fibres, suitable for use in the production of textiles, sewing, crocheting, knitting, weaving, embroidery, ...

textile
s. The most important sodium compounds are
table salt Salt is a mineral composed primarily of sodium chloride (NaCl), a chemical compound belonging to the larger class of Salt (chemistry), salts; salt in the form of a natural crystallinity, crystalline mineral is known as rock salt or halite. ...
(Na),
soda ash Sodium carbonate, , (also known as washing soda, soda ash and soda crystals) is the inorganic compound with the formula Na2CO3 and its various hydrates. All forms are white, water-soluble salts that yield moderately alkaline solutions in water. H ...
(Na2),
baking soda Sodium bicarbonate (IUPAC name: sodium hydrogencarbonate), commonly known as baking soda or bicarbonate of soda, is a chemical compound with the formula NaHCO3. It is a salt (chemistry), salt composed of a sodium cation (Sodium, Na+) and a bica ...
(Na), (NaOH),
sodium nitrate Sodium nitrate is the chemical compound with the chemical formula, formula . This alkali metal nitrate salt (chemistry), salt is also known as Chile saltpeter (large deposits of which were historically mined in Chile) to distinguish it from ord ...
(Na), di- and tri-
sodium phosphates Sodium phosphate is a generic term for a variety of salt Salt is a mineral composed primarily of sodium chloride (NaCl), a chemical compound belonging to the larger class of Salt (chemistry), salts; salt in its natural form as a crystallin ...
,
sodium thiosulfate Sodium thiosulfate (sodium thiosulphate) is an inorganic compound In chemistry Chemistry is the science, scientific study of the properties and behavior of matter. It is a natural science that covers the Chemical element, elements that make ...

sodium thiosulfate
(Na2 S2O3·5H2O), and
borax Borax, also known as sodium borate, sodium tetraborate, or disodium tetraborate, is an important boron chemical substance, compound, a mineral, and a salt (chemistry), salt of boric acid. Powdered borax is white, consisting of soft colorless c ...

borax
(Na24O7·10H2O). In compounds, sodium is usually ionically bonded to water and anions and is viewed as a hard
Lewis acid A Lewis acid (named for the American physical chemist Gilbert N. Lewis) is a chemical species that contains an empty Non-bonding orbital, orbital which is capable of accepting an electron pair from a Lewis Base (chemistry), base to form a Lewis ad ...

Lewis acid
. Most
soap Soap is a salt (chemistry), salt of a fatty acid used in a variety of cleansing and lubricating products. In a domestic setting, soaps are surfactants usually used for washing, bathing, and other types of housekeeping. In industrial settings, ...

soap
s are sodium salts of
fatty acid In chemistry Chemistry is the study of the properties and behavior of . It is a that covers the that make up matter to the composed of s, s and s: their composition, structure, properties, behavior and the changes they undergo during ...
s. Sodium soaps have a higher melting temperature (and seem "harder") than potassium soaps. Like all the
alkali metal The alkali metals consist of the chemical element Image:Simple Periodic Table Chart-blocks.svg, 400px, Periodic table, The periodic table of the chemical elements In chemistry, an element is a pure substance consisting only of atoms that ...
s, sodium reacts exothermically with water. The reaction produces caustic soda (
sodium hydroxide Sodium hydroxide, also known as lye A lye is a metal hydroxide traditionally obtained by leaching wood ashes, or a strong alkali In chemistry Chemistry is the scientific discipline involved with Chemical element, elements and chem ...

sodium hydroxide
) and flammable
hydrogen Hydrogen is the chemical element with the Symbol (chemistry), symbol H and atomic number 1. Hydrogen is the lightest element. At standard temperature and pressure, standard conditions hydrogen is a gas of diatomic molecules having the che ...

hydrogen
gas. When burned in air, it forms primarily
sodium peroxide Sodium peroxide is an inorganic compound In chemistry, an inorganic compound is typically a chemical compound that lacks carbon–hydrogen bonds, that is, a compound that is not an organic compound. However, the distinction is not clearly defined; ...
with some
sodium oxide Sodium oxide is a chemical compound A chemical compound is a chemical substance composed of many identical molecules (or molecular entity, molecular entities) composed of atoms from more than one chemical element, element held together by chemi ...
.Greenwood and Earnshaw, p. 84


Aqueous solutions

Sodium tends to form water-soluble compounds, such as
halides A halide is a binary phase, of which one part is a halogen The halogens () are a group in the periodic table consisting of five chemically related elements: fluorine Fluorine is a chemical element with the Chemical symbol, symbol F and ato ...
,
sulfate The sulfate or sulphate ion is a polyatomic anion An ion () is an atom An atom is the smallest unit of ordinary matter In classical physics and general chemistry, matter is any substance that has mass and takes up space by having ...

sulfate
s,
nitrates Nitrate is a polyatomic ion A polyatomic ion, also known as a molecular ion, is a covalently bonded set of two or more atoms, or of a metal complex, that can be considered to behave as a single unit and that has a net charge that is not ze ...
, carboxylates and
carbonate In chemistry, a carbonate is a salt Salt is a mineral composed primarily of sodium chloride (NaCl), a chemical compound belonging to the larger class of Salt (chemistry), salts; salt in its natural form as a crystallinity, crystalline mi ...

carbonate
s. The main aqueous species are the aquo complexes a(H2O)''n''sup>+, where ''n'' = 4–8; with ''n'' = 6 indicated from X-ray diffraction data and computer simulations. 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 Sodium bismuthate is an inorganic compound, and a strong oxidiser with chemical formula NaBiO3. It is somewhat hygroscopic, but not soluble in cold water, which can be convenient since the reagent can be easily removed after the reaction. It is one ...
(NaBiO3). 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 Ethanol (also called ethyl alcohol, grain alcohol, drinking alcohol, or simply alcohol) is an organic Organic may refer to: * Organic, of or relating to an organism, a living entity * Organic, of or relating to an anatomical organ (anatomy), ...

ethanol
; for example, only 0.35 g/L of sodium chloride will dissolve in ethanol.
Crown ether Crown ethers are cyclic chemical compound A chemical compound is a chemical substance A chemical substance is a form of matter In classical physics and general chemistry, matter is any substance that has mass and takes up space by havin ...

Crown ether
s, like , may be used as a
phase-transfer catalystIn chemistry Chemistry is the scientific discipline involved with Chemical element, elements and chemical compound, compounds composed of atoms, molecules and ions: their composition, structure, properties, behavior and the changes they undergo ...
. Sodium content of samples is determined by atomic absorption spectrophotometry or by potentiometry using ion-selective electrodes.


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 A coordination complex consists of a central atom or ion, which is usually metallic and is called the ''coordination centre'', and a surrounding array of chemical bond, bound molecules or ions, that are in turn known as ''ligands'' or complexing ...
(Na(NH3)6)+, with the positive charge counterbalanced by electrons as anions;
cryptand Cryptands are a family of synthetic bicyclic and polycyclic multidentate ligand In coordination chemistry, a ligand is an ion or molecule (functional group) that binds to a central metal atom to form a coordination complex. The bonding with t ...

cryptand
s permit the isolation of these complexes as crystalline solids. Sodium forms complexes with crown ethers, cryptands and other ligands. For example, 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). Cryptands, like crown ethers and other
ionophore An ionophore (from Greek#REDIRECT Greek Greek may refer to: Greece Anything of, from, or related to Greece Greece ( el, Ελλάδα, , ), officially the Hellenic Republic, is a country located in Southeast Europe. Its population is approx ...

ionophore
s, also have a high affinity for the sodium ion; derivatives of the
alkalideAn alkalide is a chemical compound A chemical compound is a chemical substance composed of many identical molecules (or molecular entity, molecular entities) composed of atoms from more than one chemical element, element held together by chemical ...
Na are obtainable by the addition of cryptands to solutions of sodium in ammonia via
disproportionation In chemistry Chemistry is the science, scientific study of the properties and behavior of matter. It is a natural science that covers the Chemical element, elements that make up matter to the chemical compound, compounds composed of atoms, mo ...

disproportionation
.


Organosodium compounds

Many organosodium compounds have been prepared. Because of the high polarity of the C-Na bonds, they behave like sources of
carbanionA carbanion is an anion An ion () is a particle, atom or molecule with a net electric charge, electrical charge. The charge of the electron is considered negative by convention. The negative charge of an ion is equal and opposite to charged ...
s (salts with organic
anion An ion () is an atom An atom is the smallest unit of ordinary matter In classical physics and general chemistry, matter is any substance that has mass and takes up space by having volume. All everyday objects that can be touched are ...
s). Some well-known derivatives include
sodium cyclopentadienide Sodium cyclopentadienide is an organosodium compound with the chemical formula, formula C5H5Na. The compound is often abbreviated as NaCp, where Cp− is the cyclopentadienide anion. Sodium cyclopentadienide is a colorless solid, although sam ...

sodium cyclopentadienide
(NaC5H5) and trityl sodium ((C6H5)3CNa).
Sodium naphthalene Sodium naphthalene is an organic salt (chemistry), salt with the chemical formula Na+C10H8−. In the research laboratory, it is used as a reductant in the synthesis of organic, organometallic, and inorganic chemistry. It is usually generated in ...
, Na+ 10H8sup>−, a strong reducing agent, forms upon mixing Na and naphthalene in ethereal solutions.


Intermetallic compounds

Sodium forms alloys with many metals, such as potassium,
calcium Calcium is a chemical element In chemistry, an element is a pure Chemical substance, substance consisting only of atoms that all have the same numbers of protons in their atomic nucleus, nuclei. Unlike chemical compounds, chemical elem ...

calcium
,
lead Lead is a chemical element In chemistry, an element is a pure Chemical substance, substance consisting only of atoms that all have the same numbers of protons in their atomic nucleus, nuclei. Unlike chemical compounds, chemical elements ...

lead
, and the group 11 and 12 elements. Sodium and potassium form KNa2 and . NaK is 40–90% potassium and it is liquid at
ambient temperature Ambient or Ambiance or Ambience may refer to: Music and sound * Ambience (sound recording)In filmmaking, ambience (also known as atmosphere, atmos, or background) consists of the sounds of a given location or space. It is the opposite of "silence" ...
. 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 Miscibility () is the property of two substances to mix in all proportions (that is, to fully dissolve in each other at any concentration In chemistry Chemistry is the study of the properties and behavior of . It is a that covers ...
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. 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 Gold is a chemical element In chemistry, an element is a pure Chemical substance, substance consisting only of atoms that all have the same numbers of protons in their atomic nucleus, nuclei. Unlike chemical compounds, chemical elemen ...

gold
(NaAu2) and
silver Silver is a chemical element In chemistry, an element is a pure Chemical substance, substance consisting only of atoms that all have the same numbers of protons in their atomic nucleus, nuclei. Unlike chemical compounds, chemical ele ...

silver
(NaAg2). Group 12 metals (
zinc Zinc is a chemical element In chemistry, an element is a pure Chemical substance, substance consisting only of atoms that all have the same numbers of protons in their atomic nucleus, nuclei. Unlike chemical compounds, chemical element ...

zinc
,
cadmium Cadmium is a chemical element In chemistry, an element is a pure Chemical substance, substance consisting only of atoms that all have the same numbers of protons in their atomic nucleus, nuclei. Unlike chemical compounds, chemical eleme ...

cadmium
and
mercury Mercury usually refers to: * Mercury (planet) Mercury is the smallest planet in the Solar System and the closest to the Sun. Its orbit around the Sun takes 87.97 Earth days, the shortest of all the Sun's planets. It is named after the Roman g ...

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.


History

Because of its importance in human health, salt has long been an important commodity, as shown by the English word ''salary'', which derives from ''salarium'', the wafers of salt sometimes given to Roman soldiers along with their other wages. In medieval Europe, a compound of sodium with the Latin name of ''sodanum'' was used as a
headache Headache is the symptom of pain Pain is a distressing feeling often caused by intense or damaging stimuli. The defines pain as "an unpleasant sensory and emotional experience associated with, or resembling that associated with, actual or ...

headache
remedy. The name sodium is thought to originate from the Arabic ''suda'', meaning headache, as the headache-alleviating properties of
sodium carbonate Sodium carbonate, ·10, (also known as Natrium Carbonate, washing soda, soda ash and soda crystals) is the inorganic compound with the formula Na2CO3 and its various hydrates. All forms are white, odourless, water-soluble salts that yield modera ...

sodium carbonate
or soda were well known in early times. Although sodium, sometimes called ''soda'', had long been recognized in compounds, the metal itself was not isolated until 1807 by
Sir Humphry Davy Sir Humphry Davy, 1st Baronet (17 December 177829 May 1829) was a Cornish Cornish is the adjective and demonym associated with Cornwall, the most southwesterly part of the United Kingdom. It may refer to: * Cornish language, a Brittonic Southw ...

Sir Humphry Davy
through the
electrolysis In chemistry Chemistry is the science, scientific study of the properties and behavior of matter. It is a natural science that covers the Chemical element, elements that make up matter to the chemical compound, compounds composed of atoms ...

electrolysis
of
sodium hydroxide Sodium hydroxide, also known as lye A lye is a metal hydroxide traditionally obtained by leaching wood ashes, or a strong alkali In chemistry Chemistry is the scientific discipline involved with Chemical element, elements and chem ...

sodium hydroxide
. In 1809, the German physicist and chemist
Ludwig Wilhelm Gilbert Ludwig Wilhelm Gilbert (12 August 1769 – 7 March 1824) was a Germany, German physicist and chemist, and professor of physics at the University of Leipzig. From 1799-1824 he published the "''Annalen der Physik''", of which Johann Christian Pog ...
proposed the names ''Natronium'' for Humphry Davy's "sodium" and ''Kalium'' for Davy's "potassium". The chemical abbreviation for sodium was first published in 1814 by
Jöns Jakob Berzelius Jöns or Jons or JONS, or ''variation'', may refer to: * Jons, commune in the Rhône department in eastern France * Jöns Jacob Berzelius (1779–1848), Swedish chemist * Jöns Budde (1435–1495), Franciscan friar from the Brigittine monastery in ...
in his system of atomic symbols, and is an abbreviation of the element's
New Latin New Latin (also called Neo-Latin or modern Latin) is the revival of Latin Latin (, or , ) is a classical language belonging to the Italic branch of the Indo-European languages. Latin was originally spoken in the area around Rome, know ...
name ''natrium'', which refers to the Egyptian ''
natron Natron is a naturally occurring mixture of sodium carbonate decahydrate (sodium carbonate, Na2CO3·10H2O, a kind of soda ash) and around 17% sodium bicarbonate (also called baking soda, NaHCO3) along with small quantities of sodium chloride and ...
'', a natural mineral salt mainly consisting of hydrated sodium carbonate. Natron historically had several important industrial and household uses, later eclipsed by other sodium compounds. Sodium imparts an intense yellow color to flames. As early as 1860, Kirchhoff and noted the high sensitivity of a sodium flame test, and stated in
Annalen der Physik und Chemie ''Annalen der Physik'' (English: ''Annals of Physics'') is one of the oldest scientific journals on physics and has been published since 1799. The journal publishes original, Peer review, peer-reviewed papers in the areas of experimental physics, ...
:
In a corner of our 60 m3 room farthest away from the apparatus, we exploded 3 mg of sodium chlorate with milk sugar while observing the nonluminous flame before the slit. After a while, it glowed a bright yellow and showed a strong sodium line that disappeared only after 10 minutes. From the weight of the sodium salt and the volume of air in the room, we easily calculate that one part by weight of air could not contain more than 1/20 millionth weight of sodium.


Occurrence

The Earth's crust contains 2.27% sodium, making it the seventh most abundant element on Earth and the fifth most abundant metal, behind
aluminium Aluminium (aluminum in and ) is a with the  Al and  13. Aluminium has a density lower than those of other common , at approximately one third that of . It has a great affinity towards , and of on the surface when exposed to air ...

aluminium
,
iron Iron () is a chemical element In chemistry Chemistry is the study of the properties and behavior of . It is a that covers the that make up matter to the composed of s, s and s: their composition, structure, properties, behav ...

iron
,
calcium Calcium is a chemical element In chemistry, an element is a pure Chemical substance, substance consisting only of atoms that all have the same numbers of protons in their atomic nucleus, nuclei. Unlike chemical compounds, chemical elem ...

calcium
, and
magnesium Magnesium is a chemical element upright=1.0, 500px, The chemical elements ordered by link=Periodic table In chemistry Chemistry is the science, scientific study of the properties and behavior of matter. It is a natural science ...

magnesium
and ahead of potassium.Greenwood and Earnshaw, p. 69 Sodium's estimated oceanic abundance is 1.08 milligrams per liter. Because of its high reactivity, it is never found as a pure element. It is found in many minerals, some very soluble, such as
halite Halite (), commonly known as rock salt, is a type of salt Salt is a mineral In geology and mineralogy, a mineral or mineral species is, broadly speaking, a solid chemical compound with a fairly well-defined chemical composition a ...

halite
and
natron Natron is a naturally occurring mixture of sodium carbonate decahydrate (sodium carbonate, Na2CO3·10H2O, a kind of soda ash) and around 17% sodium bicarbonate (also called baking soda, NaHCO3) along with small quantities of sodium chloride and ...
, others much less soluble, such as
amphibole Amphibole () is a group of Silicate minerals, inosilicate minerals, forming prism or needlelike crystals, composed of double chain tetrahedron, tetrahedra, linked at the vertices and generally containing ions of iron and/or magnesium in their s ...

amphibole
and
zeolite Zeolites are microporous, aluminosilicate Aluminosilicate mineral In geology Geology (from the Ancient Greek γῆ, ''gē'' ("earth") and -λoγία, ''-logia'', ("study of", "discourse")) is an Earth science concerned with the solid Ear ...

zeolite
. The insolubility of certain sodium minerals such as
cryolite Cryolite (Na3AlF6, sodium hexafluoroaluminate) is an uncommon mineral In geology and mineralogy, a mineral or mineral species is, broadly speaking, a solid chemical compound with a fairly well-defined chemical composition and a specific crysta ...

cryolite
and
feldspar Feldspars are a group of rock-forming aluminium tectosilicate minerals, containing sodium, calcium, potassium or barium. The most common members of the feldspar group are the ''plagioclase'' (sodium-calcium) feldspars and the ''alkali'' (potas ...
arises from their polymeric anions, which in the case of feldspar is a polysilicate.


Astronomical observations

Atomic sodium has a very strong
spectral line A spectral line is a dark or bright line in an otherwise uniform and continuous spectrum, resulting from emission or absorption of light Light or visible light is electromagnetic radiation within the portion of the electromagnetic spect ...
in the yellow-orange part of the spectrum (the same line as is used in sodium vapour street lights). This appears as an
absorption line A spectral line is a dark or bright line in an otherwise uniform and continuous spectrum, resulting from emission or absorption of light Light or visible light is electromagnetic radiation within the portion of the electromagnetic spect ...
in many types of stars, including the
Sun The Sun is the star A star is an astronomical object consisting of a luminous spheroid of plasma (physics), plasma held together by its own gravity. The List of nearest stars and brown dwarfs, nearest star to Earth is the Sun. Many othe ...

Sun
. The line was first studied in 1814 by
Joseph von Fraunhofer Joseph Ritter von Fraunhofer (; ; 6 March 1787 – 7 June 1826) was a Bavarian physicist and optical lens manufacturer. He made optical glass and achromatic telescope objective lenses, invented the spectroscope, and developed diffraction gra ...

Joseph von Fraunhofer
during his investigation of the lines in the solar spectrum, now known as the
Fraunhofer lines (nm). Dips in intensity are observed as dark lines (absorption) at the wavelengths of the Fraunhofer lines, (e.g., the features G, F, b, E, B). The "spectrum of ''blue sky''" presents across 450 – 485 nm, the wavelengths of the color ''blue''. In ...

Fraunhofer lines
. Fraunhofer named it the 'D' line, although it is now known to actually be a group of closely spaced lines split by a
fine Fine may refer to: Characters * Sylvia Fine (''The Nanny''), Fran's mother on ''The Nanny'' * Fine/Officer Fine, character in Tales from the Crypt, played by Vincent Spano Vincent M. Spano (born October 18, 1962) is an American film, stage and ...
and
hyperfine structure In atomic physics, hyperfine structure is defined by small shifts in otherwise degenerate energy levels and the resulting splittings in those energy levels of atom An atom is the smallest unit of ordinary matter In classical physics an ...
. The strength of the D line means it has been detected in many other astronomical environments. In stars, it is seen in any whose surfaces are cool enough for sodium to exist in atomic form (rather than ionised). This corresponds to stars of roughly F-type and cooler. Many other stars appear to have a sodium absorption line, but this is actually caused by gas in the foreground
interstellar medium In astronomy Astronomy (from el, ἀστρονομία, literally meaning the science that studies the laws of the stars) is a natural science that studies astronomical object, celestial objects and celestial event, phenomena. It uses math ...
. The two can be distinguished via high-resolution spectroscopy, because interstellar lines are much narrower than those broadened by
stellar rotation Stellar rotation is the angular motion of a star A star is an astronomical object consisting of a luminous spheroid of plasma Plasma or plasm may refer to: Science * Plasma (physics), one of the four fundamental states of matter * Plasma (m ...
. Sodium has also been detected in numerous
Solar System The Solar SystemCapitalization of the name varies. The International Astronomical Union, the authoritative body regarding astronomical nomenclature, specifies capitalizing the names of all individual astronomical objects but uses mixed "Sola ...

Solar System
environments, including atmosphere, the
exosphere The exosphere ( grc, ἔξω "outside, external, beyond", grc, σφαῖρα "sphere") is a thin, atmosphere-like volume surrounding a planet or natural satellite where molecules are gravitationally bound to that body, but where the density ...
of the
Moon The Moon is Earth's only natural satellite. At about one-quarter the diameter of Earth (comparable to the width of Australia (continent), Australia), it is the largest natural satellite in the Solar System relative to the size of its plane ...

Moon
, and numerous other bodies. Some
comet A comet is an icy, small Solar System body A small Solar System body (SSSB) is an object in the Solar System The Solar SystemCapitalization of the name varies. The International Astronomical Union, the authoritative body regarding astr ...

comet
s have a , which was first detected in observations of in 1997. Sodium has even been detected in the atmospheres of some
extrasolar planet An exoplanet or extrasolar planet is a planet outside the Solar System. The first possible evidence of an exoplanet was noted in 1917, but was not recognized as such. The first confirmation of detection occurred in 1992. This was followed by the ...
s via transit spectroscopy.


Commercial production

Employed only in rather specialized applications, only about 100,000 tonnes of metallic sodium are produced annually. Metallic sodium was first produced commercially in the late 19th century by carbothermal reduction of
sodium carbonate Sodium carbonate, ·10, (also known as Natrium Carbonate, washing soda, soda ash and soda crystals) is the inorganic compound with the formula Na2CO3 and its various hydrates. All forms are white, odourless, water-soluble salts that yield modera ...

sodium carbonate
at 1100 °C, as the first step of the Deville process for the production of aluminium: :Na2CO3 + 2 C → 2 Na + 3 CO The high demand for aluminium created the need for the production of sodium. The introduction of the Hall–Héroult process for the production of aluminium by Electrolysis, electrolysing a molten salt bath ended the need for large quantities of sodium. A related process based on the reduction of sodium hydroxide was developed in 1886. Sodium is now produced commercially through the
electrolysis In chemistry Chemistry is the science, scientific study of the properties and behavior of matter. It is a natural science that covers the Chemical element, elements that make up matter to the chemical compound, compounds composed of atoms ...

electrolysis
of molten
sodium chloride Sodium chloride , commonly known as salt (although sea salt also contains other chemical salt (chemistry), salts), is an ionic compound with the chemical formula NaCl, representing a 1:1 ratio of sodium and chloride ions. With Molar mass, molar ...
, based on a process patented in 1924.Pauling, Linus, ''General Chemistry'', 1970 ed., Dover Publications This is done in a Downs Cell, Downs cell in which the NaCl is mixed with calcium chloride to lower the melting point below 700 °C. As
calcium Calcium is a chemical element In chemistry, an element is a pure Chemical substance, substance consisting only of atoms that all have the same numbers of protons in their atomic nucleus, nuclei. Unlike chemical compounds, chemical elem ...

calcium
is less electropositive than sodium, no calcium will be deposited at the cathode. This method is less expensive than the previous Castner process (the electrolysis of
sodium hydroxide Sodium hydroxide, also known as lye A lye is a metal hydroxide traditionally obtained by leaching wood ashes, or a strong alkali In chemistry Chemistry is the scientific discipline involved with Chemical element, elements and chem ...

sodium hydroxide
). The market for sodium is volatile due to the difficulty in its storage and shipping; it must be stored under a dry inert gas atmosphere or anhydrous mineral oil to prevent the formation of a surface layer of
sodium oxide Sodium oxide is a chemical compound A chemical compound is a chemical substance composed of many identical molecules (or molecular entity, molecular entities) composed of atoms from more than one chemical element, element held together by chemi ...
or sodium superoxide.


Uses

Though metallic sodium has some important uses, the major applications for sodium use compounds; millions of tons of
sodium chloride Sodium chloride , commonly known as salt (although sea salt also contains other chemical salt (chemistry), salts), is an ionic compound with the chemical formula NaCl, representing a 1:1 ratio of sodium and chloride ions. With Molar mass, molar ...
, sodium hydroxide, hydroxide, and sodium carbonate, carbonate are produced annually. Sodium chloride is extensively used for anti-icing and de-icing and as a preservative; examples of the uses of sodium bicarbonate include baking, as a raising agent, and sodablasting. Along with potassium, many important medicines have sodium added to improve their bioavailability; though potassium is the better ion in most cases, sodium is chosen for its lower price and atomic weight. Sodium hydride is used as a base for various reactions (such as the aldol reaction) in organic chemistry, and as a reducing agent in inorganic chemistry. Metallic sodium is used mainly for the production of sodium borohydride, sodium azide, indigo dye, indigo, and triphenylphosphine. A once-common use was the making of tetraethyllead and titanium metal; because of the move away from TEL and new titanium production methods, the production of sodium declined after 1970.Alfred Klemm, Gabriele Hartmann, Ludwig Lange, "Sodium and Sodium Alloys" in Ullmann's Encyclopedia of Industrial Chemistry 2005, Wiley-VCH, Weinheim. Sodium is also used as an alloying metal, an anti-scaling agent, and as a reducing agent for metals when other materials are ineffective. Note the free element is not used as a scaling agent, ions in the water are exchanged for sodium ions. Sodium vapor lamp, Sodium plasma ("vapor") lamps are often used for street lighting in cities, shedding light that ranges from yellow-orange to peach as the pressure increases. By itself or NaK, with potassium, sodium is a desiccant; it gives an intense blue coloration with benzophenone when the desiccate is dry. In organic synthesis, sodium is used in various reactions such as the Birch reduction, and the sodium fusion test is conducted to qualitatively analyse compounds. Sodium reacts with alcohol and gives alkoxides, and when sodium is dissolved in ammonia solution, it can be used to reduce alkynes to trans-alkenes. Lasers emitting light at the sodium D line are used to create artificial laser guide stars that FASOR (laser physics), assist in the adaptive optics for land-based visible-light telescopes.


Heat transfer

Liquid sodium is used as a Coolant, heat transfer fluid in sodium-cooled fast reactor, some types of nuclear reactorsSodium as a Fast Reactor Coolant
presented by Thomas H. Fanning. Nuclear Engineering Division. U.S. Department of Energy. U.S. Nuclear Regulatory Commission. Topical Seminar Series on Sodium Fast Reactors. 3 May 2007
because it has the high thermal conductivity and low neutron absorption cross section (physics), cross section required to achieve a high neutron flux in the reactor. The high boiling point of sodium allows the reactor to operate at ambient (normal) pressure, but the drawbacks include its opacity, which hinders visual maintenance, and its explosive properties. Radioactive sodium-24 may be produced by neutron activation, neutron bombardment during operation, posing a slight radiation hazard; the radioactivity stops within a few days after removal from the reactor. If a reactor needs to be shut down frequently, is used; because NaK is a liquid at room temperature, the coolant does not solidify in the pipes. In this case, the pyrophoricity of potassium requires extra precautions to prevent and detect leaks. Another heat transfer application is poppet valves in high-performance internal combustion engines; the valve stems are partially filled with sodium and work as a heat pipe to cool the valves.


Biological role


Biological role in humans

In humans, sodium is an essential mineral that regulates blood volume, blood pressure, Osmosis, osmotic equilibrium and pH. The minimum physiological requirement for sodium is estimated to range from about 120 milligrams per day in newborns to 500 milligrams per day over the age of 10.


Diet

Sodium chloride is the principal source of sodium in the diet, and is used as seasoning and preservative in such commodities as pickling, pickled preserves and Jerky (food), jerky; for Americans, most sodium chloride comes from Convenience food, processed foods. Other sources of sodium are its natural occurrence in food and such food additives as monosodium glutamate (MSG), sodium nitrite, sodium saccharin,
baking soda Sodium bicarbonate (IUPAC name: sodium hydrogencarbonate), commonly known as baking soda or bicarbonate of soda, is a chemical compound with the formula NaHCO3. It is a salt (chemistry), salt composed of a sodium cation (Sodium, Na+) and a bica ...
(sodium bicarbonate), and sodium benzoate. The U.S. Institute of Medicine set its Dietary Reference Intake, tolerable upper intake level for sodium at 2.3 grams per day, but the average person in the United States consumes 3.4 grams per day. The American Heart Association recommends no more than 1.5 g of sodium per day.


High sodium consumption

High sodium consumption is unhealthy, and can lead to alteration in the mechanical performance of the heart. High sodium consumption is also associated with chronic kidney disease, high blood pressure, cardiovascular diseases, and stroke.


= High blood pressure

= There is a strong correlation between higher sodium intake and higher blood pressure. Studies have found that lowering sodium intake by 2 g per day tends to lower systolic blood pressure by about two to four mm Hg. It has been estimated that such a decrease in sodium intake would lead to between 9 and 17% fewer cases of hypertension. Hypertension causes 7.6 million premature deaths worldwide each year. (Note that salt contains about 39.3% sodiumthe rest being chlorine and trace chemicals; thus, 2.3 g sodium is about 5.9 g, or 5.3 ml, of saltabout one US teaspoon.) One study found that people with or without hypertension who excreted less than 3 grams of sodium per day in their urine (and therefore were taking in less than 3 g/d) had a ''higher'' risk of death, stroke, or heart attack than those excreting 4 to 5 grams per day. Levels of 7 g per day or more in people with hypertension were associated with higher mortality and cardiovascular events, but this was not found to be true for people without hypertension. The Food and Drug Administration, US FDA states that adults with hypertension and prehypertension should reduce daily sodium intake to 1.5 g.


Physiology

The renin–angiotensin system regulates the amount of fluid and sodium concentration in the body. Reduction of blood pressure and sodium concentration in the kidney result in the production of renin, which in turn produces aldosterone and angiotensin, which stimulates the reabsorption of sodium back into the bloodstream. When the concentration of sodium increases, the production of renin decreases, and the sodium concentration returns to normal. The sodium ion (Na+) is an important electrolyte in neuron function, and in osmoregulation between cells and the
extracellular fluid In cell biology Cell biology (also cellular biology or cytology) is a branch of biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, ...
. This is accomplished in all animals by Na+/K+-ATPase, Na+/K+-ATPase, an active transporter pumping ions against the gradient, and sodium/potassium channels. Sodium is the most prevalent metallic ion in extracellular fluid. In humans, unusually low or high sodium levels in the blood is recognized in medicine as hyponatremia and
hypernatremia Hypernatremia, also spelled hypernatraemia, is a high concentration of sodium in the Serum (blood), blood. Early symptoms may include a strong feeling of thirst, weakness, nausea, and anorexia (symptom), loss of appetite. Severe symptoms include de ...
. These conditions may be caused by genetic factors, ageing, or prolonged vomiting or diarrhea.


Biological role in plants

In C4 plants, sodium is a micronutrient that aids metabolism, specifically in regeneration of phosphoenolpyruvic acid, phosphoenolpyruvate and synthesis of chlorophyll. In others, it substitutes for
potassium Potassium is a chemical element upright=1.0, 500px, The chemical elements ordered by link=Periodic table In chemistry Chemistry is the science, scientific study of the properties and behavior of matter. It is a natural science ...

potassium
in several roles, such as maintaining turgor pressure and aiding in the opening and closing of stomata. Excess sodium in the soil can limit the uptake of water by decreasing the water potential, which may result in plant wilting; excess concentrations in the cytoplasm can lead to enzyme inhibition, which in turn causes necrosis and chlorosis. In response, some plants have developed mechanisms to limit sodium uptake in the roots, to store it in cell vacuoles, and restrict salt transport from roots to leaves; excess sodium may also be stored in old plant tissue, limiting the damage to new growth. Halophytes have adapted to be able to flourish in sodium rich environments.


Safety and precautions

Sodium forms flammable hydrogen and caustic
sodium hydroxide Sodium hydroxide, also known as lye A lye is a metal hydroxide traditionally obtained by leaching wood ashes, or a strong alkali In chemistry Chemistry is the scientific discipline involved with Chemical element, elements and chem ...

sodium hydroxide
on contact with water; ingestion and contact with moisture on skin, eyes or mucous membranes can cause severe burns. Sodium spontaneously explodes in the presence of water due to the formation of hydrogen (highly explosive) and sodium hydroxide (which dissolves in the water, liberating more surface). However, sodium exposed to air and ignited or reaching autoignition (reported to occur when a molten pool of sodium reaches about ) displays a relatively mild fire. In the case of massive (non-molten) pieces of sodium, the reaction with oxygen eventually becomes slow due to formation of a protective layer. Fire extinguishers based on water accelerate sodium fires; those based on carbon dioxide and bromochlorodifluoromethane should not be used on sodium fire. Metal fires are Fire extinguisher, Class D, but not all Class D extinguishers are effective when used to extinguish sodium fires. An effective extinguishing agent for sodium fires is Met-L-X. Other effective agents include Lith-X, which has graphite powder and an organophosphate flame retardant, and dry sand. Sodium fires are prevented in nuclear reactors by isolating sodium from oxygen with surrounding sodium pipes containing inert gas. Pool-type sodium fires are prevented using diverse design measures called catch pan systems. They collect leaking sodium into a leak-recovery tank where it is isolated from oxygen.


See also


References


Bibliography

*


External links


Sodium
at ''The Periodic Table of Videos'' (University of Nottingham)
Etymology of "natrium" – source of symbol Na




{{Authority control Sodium, Chemical elements Alkali metals Sodium minerals Desiccants Dietary minerals Biology and pharmacology of chemical elements Reducing agents Nuclear reactor coolants Chemical elements with body-centered cubic structure