Sodium | Sodium Description, Chemical Properties and Uses

Sodium | Sodium Description, Chemical Properties and Uses


Sodium (Na) is a chemical element of the alkali metal group with the atomic number 11 and the Atomic symbol is Na. The most common alkali metal is sodium, which is soft and silvery-grey. It is easily cuttable with a well-bladed knife. 2.27% of the earth's crust is made up of it. Sir Humphry Davy employed fused caustic soda to electrolyze it in order to isolate it in 1807. It is seldom seen free in nature since it is reactive. Common salt is the most significant sodium compound that may be found in nature (NaCl). It is also referred to as table salt, lake salt, rock salt, sea salt, and common salt. Sodium chloride makes up 2.0–2.9% of seawater. Sodium chloride is used to make sodium metal and other sodium compounds. Natural sodium compounds that are also significant include:

(i) Chile Saltpetre, NaNO₃

(ii) Glauber's salt, Na₂SO₄10H₂O

(iii) Trona, Na₂CO₃.2NaHCO₃-3H₂O

(iv) Natron, Na₂CO₃-H₂O

(v) Tincal (Borax), Na₂B₄O₇-10H₂O

(vi) Cryolite, Na₃AlF₆

(vii) Soda feldspar, NaAlSi,O8

Extraction process

Sodium is obtained on large scale by two processes:

(i) Castner's process

(ii) Down's process

(i) Castner's process: In this process, electrolysis of fused sodium hydroxide is carried out at 330°C using iron as cathode and nickel as anode.

2NaOH2Na+ + 20H-

At cathode: 2Na+ + 2e2Na

At anode : 40H-⇋2H₂O+ O₂+ 4e

During the electrolysis process, oxygen and water are produced. Water formed at the anode gets from which some partly evaporated and some is partly broken down and hydrogen is discharged at cathode.

H₂OH⁺+ OH⁻

At cathode: 2H+ 2e2HH

(ii) Down'socess: These days, sodium metal is produced using this method. At a temperature of around 600 °C, which is the melting point of the mixture, iron is employed as the cathode and graphite is used as the anode to electrolyze fused sodium chloride that also contains calcium chloride and potassium fluoride.

Calcium chloride is combined with sodium chloride and melted. Sodium chloride can be made from rock salt or sea water. To lower the operating temperature of the cell from 801°C (the melting point of sodium chloride) to 600°C, calcium chloride is added to the sodium chloride electrolyte (the melting point of the mixture). This reduces the need for electrical energy, making the procedure more cost-effective.

The graphite Anode is surrounded by a steel cathode. Sodium and chlorine would forcefully combine at 600 °C to make sodium chloride again. The Down's cell has a steel gauze around the graphite anode to keep it and the cathode apart to avoid this happening. On the electrolyte, the molten sodium floats and is run off for storage. The calcium ions' attraction to the cathode, where they create calcium metal, presents a challenge, though. As a result, there is a substantial amount of calcium in the sodium runoff. Fortunately, when the combination cools, the calcium crystallises out, leaving behind comparatively pure sodium metal.

About 60,000 to 80,000 tonnes of sodium metal are produced annually throughout the world.

NaCINa⁺+ Cl⁻ is the total reaction that occurs in the cell.

At cathode:

Na+ eNa

At anode : 2Cl Cl+ 2e

The following challenges arise during pure NaCl electrolysis:

(a) NaCl has a high fusion temperature of 801°C. Both salt and chlorine are corrosive at this temperature.

(b) When sodium reaches this temperature, a metallic fog emerges. By adding CaCl₂ and KF, the fusion temperature is lowered from 801°C to 600°C to overcome the aforementioned issues. This approach is less expensive, and chlorine is a byproduct.

Properties of Sodium

Physical Properties of Sodium

(a) The metal is a silvery white colour when it is first cut, but exposure to air causes the surface to tarnish quickly. Na is the sodium isotope that is the most stable. There are numerous sodium radioactive isotopes known, including Na, Na, Na, Na, and Na. Na has the shortest half life of them (0.02 seconds).

(b) It is lighter than water and soft in nature.

(c) It has a ductile and malleable character.

(d) It is a good heat and electrical conductor.

(e) Its melting point is low. Just below the typical boiling point of water, at 371 K or 97.8°C, it melts, and its boiling point is 1156 K.

(f) It creates an amalgam when mixed with mercury.

(g) It dissolves in liquid ammonia to create a solution that is a deep blue colour.

(h) In the yellow part of the spectrum, it produces the two brilliant lines D, (589.2 nm) and D2 (590.4 nm).

Chemical Properties of Sodium

(a) Reactivity to air: When kept in a humid environment, it starts to lose its shine due to the production of oxide, hydroxide, and carbonate.

It is constantly stored under kerosene because the airborne water vapour it reacts with causes it to rust quickly. It transforms into a combination of Na2O and Na2O2 upon heating in air or oxygen. Oxone is the name given to N2O in industry.

4Na+ O2→2NaO

4Na+ 2O₂→2Na₂O2 (Sodium peroxide)

The peroxide ion, O acts as an oxidizing agent.

(b) Water reactivity: It vigorously breaks down water while producing heat and hydrogen. The hydrogen can catch fire occasionally,

2Na+ 2H₂O→2NaOH + H₂

(c) Acid reactivity: It has a strong electro-positive character, is easily depleted of electrons, and is transformed into monovalent ions, Nat. As a result, it easily removes hydrogen from acids and produces the equivalent salts.

2Na+ 2HC12NaCl + H₂

(d) It has a strong affinity for non-metallic materials. With the exception of hydrogen, halogens, sulphur, phosphorus, and others, it instantly interacts to generate the appropriate compounds when heated.

2Na+ H2 300°C→2NaH

2Na+ Cl₂→2NaCl

2Na+ S→Na₂S

3Na+ P→Na₃P

Graphite anode

(e) Reducing agent: Due to its high oxidation potential and low ionisation potential, it functions as a vigorous reducer.

SiO₂ + 4Na→Si + 2Na₂O

3CO₂+ 4Na→C + 2Na₂CO₃

Al₂O₃ + 6Na→2A1 + 3Na2O

BeCl₂ + 2Na→Be+ 2NaCl

(f) Ammonia reactivity: Sodamide is produced with the release of hydrogen when dry ammonia is passed over sodium at 300–400°C in the absence of air.

2Na+ 2NH₃→2NaNH₂ + H₂

Sodamide is a waxy solid and is used for making a number of sodium compounds.

Uses of Sodium

Sodium is used:

(i) Sodium is widely used in the manufacture of various chemicals like sodium peroxide (Na2O2), sodamide (NaNH2), sodium cyanide (NaCN), etc.

(ii) Sodium is used for making lead tetraethyl (used as antiknock properties in petrol).

4C2H5Cl + 4Na-Pb → (C2Hs)₄+Pb+ 3Pb+ 4NaCl

(iii) Sodium is also used in the preparation of sodium amalgam (used as a reducing agent).

(iv) sodium is used as molten state in nuclear reactors as heat transfer medium.

(v) Sodium is in sodium vapour lamps which emit yellow light.

(vi) Sodium used as a laboratory reagent for organic analysis. 

(vii) It is used in manufacturing of high temperature thermometers in the form of sodium potassium alloy.

(viii) It is used for the extraction of C, Be, Mg and Si.

(ix) largely as a reducing agent in industry for the production of artificial rubber, dyes, pharmaceutical drugs, etc.

(x) for filling exhaust valves of aeroplane engines on account of its lightness and high thermal conductivity.

(xi) as a liquid coolant in nuclear power stations. (xii) molten sodium metal is used to produce zirconium and titanium from their chloride.

 A TiCl4(g) + 4Na →4NaCl(s) + Ti(s)


Many compound of sodium can be formed with reaction to different types of elements:

1. Sodium Oxide, Na₂O

2. Sodium Peroxide, Na₂O₂

3. Sodium Hydroxide, NaOH

4. Sodium Carbonate, NaCO₃.10H₃O

5. Sodium Bicarbonate (Baking Soda), NaHCO₃

6. Sodium Thiosulphate (Hypo), Na₂S₂3.5H₃O

7. Microcosmic Salt, Na(NH₄)HPO₄.4H₂O

8. Sodium Chloride, NaCl

9. Sodium Cyanide, NaCN

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