Sodium

Sodium







Overview
Physical Characteristics
Chemical Characteristics
Commercial production
Isotopes
Applications of Free element
Other applications, specially Heat transfering
Compounds
Precautions
Popular reactions
Specieal characteristics of sodium


Overview
*electronic configuration 1S² 2S²2P⁶ 3S¹
*Sodium is a chemical element with the symbol Na (from Latin: natrium) in the periodic table and atomic number 11.
*It is a soft, silvery-white, highly reactive metal and is a member of the alkali metals; its only stable isotope is ²³Na.
*The free metal does not occur in nature, but instead must be prepared from its compounds; it was first isolated by Humphry *Davy in 1807 by the electrolysis of sodium hydroxide.
*Sodium is the sixth most abundant element in the Earth's crust, and exists in numerous minerals such as

• feldspars,
• sodalite and
• rock salt.

Atomic structure

*Many salts of sodium are highly water-soluble, and their sodium has been leached by the action of water so that chloride and sodium are the most common dissolved elements by weight in the Earth's bodies of oceanic water.
*Many sodium compounds are useful, such as
sodium hydroxide (lye) for soapmaking, and
sodium chloride for use as a deicing agent and a nutrient (edible salt). Sodium is an essential element for all animals and some plants.
*In animals, sodium ions are used against potassium ions to build up charges on cell membranes, allowing transmission of nerve impulses when the charge is dissipated.
The consequent need of animals for sodium causes it to be classified as a dietary inorganic macro-mineral.


Physical Characteristics
*Sodium at standard temperature and pressure is a soft metal that can be readily cut with a knife and is a good conductor of electricity.

How soften it is

*Freshly exposed, sodium has a bright, silvery luster that rapidly tarnishes, forming a white coating of sodium hydroxide and sodium carbonate.
*These properties change at elevated pressures: at 1.5 Mbar, the color changes to black, then to red transparent at 1.9 Mbar, and finally clear transparent at 3 Mbar.
*All of these allotropes are insulators and electrides.
When sodium or its compounds are introduced into a flame, they turn it yellow,

Na when introduced to flame

because the excited 3s electrons of sodium emit a photon when they fall from 3p to 3s; the wavelength of this photon corresponds to the D line at 589.3 nm.
*Spin-orbit interactions involving the electron in the 3p orbital split the D line into two; hyperfine structures involving both orbitals cause many more lines.



Chemical Characteristics
*Sodium is generally less reactive than potassium and more reactive than lithium.
*Like all the alkali metals, it reacts exothermically with water, to the point that sufficiently large pieces melt to a sphere and may explode; this reaction produces caustic sodium hydroxide and flammable hydrogen gas.

Reaction with water

*When burned in dry air, it mainly forms sodium peroxide as well as some sodium oxide.
*In moist air, sodium hydroxide results.

• Here are main reactions happen when a piece of sodium opened to air:

1.  Na_(s) + O_2(g) → Na₂O_(s)
2.  Na_(s) + H₂O_{(g / l )} → NaOH_(aq) + H_2(g)
3.  Na₂O_(s) + H₂O_{(g / l)} → NaOH_(aq)
4.  NaOH_(aq) + CO_2(g) → Na₂CO_3(s) + H₂O_(l)
5.  NaOH_(aq) + CO_2(g) + H₂O_(g/l) → NaHCO_3(aq)

*Sodium metal is highly reducing, with the reduction of sodium ions requiring −2.71 volts but potassium and lithium have even more negative potentials.
 *Hence, the extraction of sodium metal from its compounds (such as with sodium chloride) uses a significant amount of energy.


Isotopes
*20 isotopes of sodium are known, but only ²³Na is stable.
Two radioactive, cosmogenic isotopes are the byproduct of cosmic ray spallation: ²²Na with a half-life of 2.6 years and ²⁴Na with a half-life of 15 hours; all other isotopes have a half-life of less than one minute.
*Two nuclear isomers have been discovered, the longer-lived one being ²⁴mNa with a half-life of around 20.2 microseconds.
Acute neutron radiation, such as from a nuclear criticality accident, converts some of the stable ²³Na in human blood to ²⁴Na; by measuring the concentration of 24Na in relation to ²³Na, the neutron radiation dosage of the victim can be calculated.



Commercial production
*Enjoying rather specialized applications, only about 100,000 tonnes of metallic sodium are produced annually.
Metallic sodium was first produced commercially in 1855 by carbothermal reduction of sodium carbonate at 1100 °C[citation needed], in what is known as the Deville process:

    Na₂CO₃ + 2 C → 2 Na + 3 CO

*A related process based on the reduction of sodium hydroxide was developed in 1886.
*Sodium is now produced commercially through the electrolysis of molten sodium chloride, based on a process patented in 1924.

At Cathode:

    Na⁺_(l) + e →Na_(l)

At Anode:

    2Cl^-_(l) → Cl_2(g) + 2e

*This is done in a Downs Cell in which the NaCl is mixed with calcium chloride to lower the melting point below 700 °C.
As calcium is less electropositive than sodium, no calcium will be deposited at the cathode.
*This method is less expensive than the previous Castner process of electrolyzing sodium hydroxide.

*Reagent-grade sodium in tonne quantities sold for about US$3.
30/kg in 2009; lower purity metal sells for considerably less.
*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 or sodium superoxide.
*These oxides can react violently in the presence of organic materials. Sodium will also burn violently when heated in air.
*Smaller quantities of sodium cost far more, in the range of US$165/kg; the high cost is partially due to the expense of shipping hazardous material.



Applications of Free element
Metallic sodium is mainly used for the production of

• sodium borohydride,
• sodium azide,
•  indigo, and
•  triphenylphosphine.

Previous uses were for the

• making of tetraethyllead and
• titanium metal;

•  because applications for these chemicals were discontinued, the production of sodium declined after 1970.
• Sodium is also used as
• an alloying metal,
• an anti-scaling agent, and as a reducing agent for metals when other materials are ineffective.
• Sodium vapor lamps are often used for street lighting in cities and give colours ranging from yellow-orange to peach as the pressure increases.

*By itself or with potassium, sodium is a desiccant; it gives an intense blue colouration 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. Lasers emitting light at the D line, utilising sodium, are used to create artificial laser guide stars that assist in the adaptive optics for land-based visible light telescopes.

Other applications, specially Heat transfering
*Liquid sodium is used as a heat transfer fluid in some fast reactors,due to its high thermal conductivity and low neutron absorption cross section, which is required to achieve a high neutron flux; the high boiling point allows the reactor to operate at ambient pressure.
*Drawbacks of using sodium include its opacity, which hinders visual maintenance, and its explosive properties. Radioactive sodium-24 may be formed by neutron activation 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 frequently shut down, NaK is used; due to it being liquid at room temperature, cooling pipes do not freeze.
In this case, the pyrophoricity of potassium means extra precautions against leaks need to be taken.
*Another heat transfer application is in high-performance internal combustion engines with poppet valves, where valve stems partially filled with sodium are used as a heat pipe to cool the valves.


Compounds
Sodium compounds are of immense commercial importance, being particularly central to industries producing

• glass,
• paper,
• soap, and
• textiles.

The sodium compounds that are the most importantinclude

• table salt (NaCl),
• soda ash (Na₂CO₃),
• baking soda (NaHCO₃),
• caustic soda (NaOH),
• sodium nitrate (NaNO₃),
• di- and tri-sodium phosphates,
• sodium thiosulfate (Na₂S₂O₃·5H₂O), and
• borax (Na₂B₄O₇·10H₂O).

Na storage

*In its compounds, sodium is usually ionically bonded to water and anions, and is viewed as a hard Lewis acid.
*Two equivalent images of the chemical structure of sodium stearate, a typical soap.



Precautions
*Care is required in handling elemental sodium, as it generates inflammable hydrogen and caustic sodium hydroxide upon contact with water; powdered sodium may combust spontaneously in air or oxygen.
*Excess sodium can be safely removed by hydrolysis in a ventilated cabinet; this is typically done by sequential treatment with isopropanol, ethanol and water.
Isopropanol reacts very slowly, generating the corresponding alkoxide and hydrogen.

*Fire extinguishers based on water accelerate sodium fires; those based on carbon dioxide and bromochlorodifluoromethane lose their effectiveness when they dissipate.
*An effective extinguishing agent is Met-L-X, which comprises approximately 5% Saran in sodium chloride together with flow agents; it is most commonly hand-applied with a scoop.
*Other materials include Lith+, which has graphite powder and an organophosphate flame retardant, and dry sand. 
*Most soaps are sodium salts of fatty acids.
*Sodium soaps are harder (higher melting) soaps than potassium soaps.
*Sodium chloride is extensively used for anti-icing and de-icing and as a preservative; sodium bicarbonate is mainly used for cooking.
*Along with potassium, many important medicines have sodium added to improve their bioavailability; although in most cases potassium is the better ion, sodium is selected 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.( you may learn aldol reaction under Organic chamistry )



Popular reactions
1) Na_(s) + O_2(g) → Na₂O_(s)
2) Na_(s) + H₂O_{(g / l )}→ NaOH_(aq) + H_2(g)
3) Na₂O_(s) + H₂O_{(g / l)→} NaOH_(aq)
4) NaOH_(aq) + CO_2(g)→ Na₂CO_3(s) + H₂O_(l)
5) NaOH_(aq) + CO_2(g) + H₂O_(g/l)→ NaHCO_3(aq)
(When kept in air)

6) Na_(s) + S_(s) → Na₂S_(s)
7) Na_(s) + F_2(g) (halogens) → NaF_(s)
8) Na_(s) + P_(s) → Na₃P_(s)

Reaction with water

9) Na_(s) + HCl_(aq) → NaCl_(aq) + H_2(g)
10)Na_(s) + H₂SO_4(aq) → Na₂SO_4(aq) + H_2(g)
note: Na_(s) when reacts with an acid it turns to salt of metal and reduces Hydrogen gas.for a example think an acid called " HX "
if it reacts with Na_(s) :
Na_(s) + HX_(aq) → NaX + H_2(g)


11)Na_(s) + NaOH_(l) → Nothing happens
12)Na_(s) + NaOH_(aq) → NaOH_(aq) + H_2(g)
Note: The NaOH liquid (first) doesn't include free H⁺ / OH^- ions as it doesn't contain water.
The NaOH aqueous solution it contains water and so that H⁺ / OH^- contain.


13)Na_(s) + CH₃COOH_(aq) → CH₃COONa_(aq) + H_2(g)
(you will learn these types of reactions under organic chemistry)










Specieal characteristics of sodium

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Atomic properties
Oxidation states	+1, -1 (strongly basic oxide)
Electronegativity	0.93 (Pauling scale)
Ionization energies (more)	1st: 495.8 kJ·mol−1
	2nd: 4562 kJ·mol−1
	3rd: 6910.3 kJ·mol−1
Atomic radius	186pm
Covalent radius	166±9pm
Van der Waals radius	227 pm
General properties
Name, symbol, number	sodium, Na, 11
Pronunciation	/soʊdiəm/SOH-dee-əm
Element category	alkali metal
Group, period, block	1, 3, s
Standard atomic weight	22.98976928(2)

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