Sodium: Physical and Chemical Properties, Reactions, and Uses

Sodium is a chemical element belonging to the Alkali metal group of the periodic table. Its symbol is Na and its atomic number is 11.

• It is a highly reactive alkali metal and it is not found as a free element in nature and is usually prepared from different compounds.
• Sodium is the sixth most abundant element in the earth’s crust and is found in various minerals such as sodalite, feldspars, and rock salts. 
• It is an essential element for all plants and animals as it serves as the main cation in the extracellular fluids (ECF).
• It is a major contributor to the ECF osmotic pressure and ECF compartment volume.
• In the nerve cells, sodium is the key player for transmission of the nerve impulse i.e. the action potential.
• Sodium was discovered by Humphry Davy.

Key Terms: Element, Periodic Table, Alkali metal, Earth’s crust, Minerals, Sodalite, Feldspars, Rock salts, Isotopes, Lithium, Potassium, Oxygen, Chemical reactions, Atomic number, Electronic configuration

What is Sodium?

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Sodium belongs to the Group 1 of the periodic table along with Lithium (Li) and Potassium (K). It is a very soft, silvery-white but highly reactive metal. That is why it is not found as a free element in nature.

• It is a chemical element having the symbol of ‘Na’.
• The atomic number of sodium is 11.
• Sodium contains 11 electrons in its atomic structure with an electron configuration of 1s² 2s² 2p⁶ 3s¹.
• It reacts fiercely with water vapor, water, and snow to produce sodium hydroxide which is a strong alkaline substance.
• When metallic sodium is exposed to air it reacts with the oxygen of the air to produce a thin layer of sodium oxide.
• Therefore, it loses its silvery appearance and becomes silvery-grey due to the presence of sodium oxide.

Sodium

Occurrence of Sodium

The Earth’s crust contains almost 2.27% sodium, making it the sixth most abundant element on the Earth and the fifth most abundant metal on the planet.

• Because of its high reactivity, it is not found in the pure form.
• It is found in many minerals, some of them are soluble (for example- Natron) and some of them are very less soluble in water (Example- Zeolite).

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Physical Properties of Sodium

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The following are the physical properties of Sodium

• Sodium has a bright metallic luster.
• In color, it is very similar to silver.
• It is soft enough at normal temperatures to be formed into leaves with the pressure of the finger.
• Sodium compounds tarnish quickly when exposed to air, however not as quickly as potassium.
• Sodium combines with oxygen in the air to produce sodium oxide, which then reacts with water vapor in the air to produce a sodium hydroxide film.

Chemical Properties of Sodium

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The following are the chemical properties of Sodium

Isotopes of Sodium

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There are 20 isotopes of sodium are known to date. However, ²³Na is stable. Other isotopes are highly unstable with some of them having a half-life of less than a minute.

The main isotopes of sodium are given below:

Reactions of Sodium

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The following are the reactions of sodium

Reaction with Air

Sodium is normally a highly reactive metal. It reacts with oxygen to form sodium oxide which is relatively less reactive.

• Its reaction with oxygen can be accelerated by the presence of impurities in it.
• Sodium also reacts with water vapor or moisture to form a sodium hydroxide layer.
• This in turn absorbs carbon dioxide to form sodium bicarbonate and does not react with nitrogen.
• This is the reason why sodium is kept in nitrogen or some other inert gases or oils.
• Sodium is more reactive in the air as a liquid than a solid.
• Liquid sodium can ignite at 125 °C. Sodium burns softly in a dry setting emitting a cloud of white smoke.

Reaction with Nonmetals

Usually, alkali metals are involved in reactions with halogens. The degree of reactivity increases or decreases with the atomic weight of the halogen. Sodium is no exception.

• Under certain conditions, halogens and sodium vapors react to exhibit chemiluminescence.
• Halogen acids like hydrochloric acid react fiercely with sodium to form sodium halides. The reaction is highly exothermic.
• Sodium also reacts with strong metal acids to produce corresponding salts.
• In a reaction with nitric acid fumes at 15°c, sodium produces sodium nitrate.
• In reaction with sulfuric and acetic acid sodium produces sodium sulfate and sodium acetate.
• It reacts with molten sulfur to form polysulfides.
• Liq. Tellurium and Selenium vigorously react with sodium (solid) to produce tellurides and selenides respectively.

Reaction with Organic Compounds

The reaction of sodium with organic compounds is well-studied. Sodium reacts with anhydrous alcohols to alkoxides.

Na + ROH → RONa + 1/2 H₂

The reaction is most vigorous with methanol and the reactivity decreases with increasing alcohol’s molecular weight.

• Upon reaction with excess methanol, sodium produces sodium methoxide.
• Organic acids react with sodium to produce sodium salts.

Reaction with metals

Sodium is miscible with other alkali metals such as rubidium, cesium, and potassium. A eutectic melting at a temperature of −10 °C takes place in the sodium-potassium system and is commercially known as NaK.

• It can be used as a heat-transfer fluid as well as an organic reactant.
• The eutectics are produced in the sodium-caesium and the sodium-rubidium binary systems melt, at −30 °C and −4.5 °C, respectively.
• Sodium is a minor component with cesium and potassium of the ternary alloy NaKCs, whose melting temperature is −78 °C.

Commercial Production of Sodium

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The commercial production of metallic sodium started in the 19^th century.

• The reaction was a carbothermal reaction of sodium carbonate at 1100 °C. at the first step of aluminum production.
• In modern days, sodium is commercially produced from molten sodium chloride by the process of electrolysis.
• Another process that can be employed is the Castner process in which electrolysis of sodium hydroxide is done.

Uses of Sodium

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The use of metallic sodium is quite limited; the major uses of the sodium use compound. The compounds like sodium chloride, hydroxide, and carbonates are produced in millions of tons every year.

• Sodium chloride is mainly used for anti-icing and de-icing and as a preservative.
• Sodium is used in improving the structure of certain alloys, soaps, purification of molten metals, and vapor lamps.
• It is important in the making of organic compounds and in making esters.
• Sodium hydride is used in various reactions in organic chemistry and is used as a reducing agent in inorganic chemistry.
• Sodium plasma (vapor) lamps are often used for street lighting in cities.
• In organic reactions, sodium is used for the Birch reaction.
• Lasers emitting lights at the sodium D line are used to make artificial laser guide stars which are used in visible-light telescopes.

Things to Remember

• Sodium is a chemical element having a symbol of ‘Na’ and an atomic number of 11.
• It belongs to the Group 1 of alkali metals of the periodic table.
• Sodium is a very soft, silvery-white but highly reactive metal
• It contains 11 electrons in its atomic structure with an electron configuration of 1s²2s²2p⁶3s¹
• Sodium does not react with nitrogen. This is the reason why sodium is kept in nitrogen or some other inert gases or oils.
• Under certain conditions, halogens and sodium vapors react to exhibit chemiluminescence.
• Halogen acids like hydrochloric acid react fiercely with sodium to form sodium halides.
• Sodium chloride is mainly used for anti-icing and de-icing and as a preservative.

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