Sodium

Sodium: the essentials

 Brief description: sodium is a Group 1 element (or IA in older labelling styles). Group 1 elements are often referred to as the "alkali metals". The chemistry of sodium is dominated by the +1 ion Na⁺. Sodium salts impart a characteristic orange/yellow colour to flames and orange street lighting is orange because of the presence of sodium in the lamp.

Soap is generally a sodium salt of fatty acids. The importance of common salt to animal nutrition has been recognized since prehistoric times. The most common compound is sodium chloride, (table salt).

Table: basic information about and classifications of sodium.

Name: Sodium Symbol: Na Atomic number: 11 Atomic weight: 22.98976928 (2) Standard state: solid at 298 K CAS Registry ID: 7440-23-5

Group in periodic table: 1 Group name: Alkali metal Period in periodic table: 3 Block in periodic table: s-block Colour: silvery white Classification: Metallic

The result of adding different metal salts to a burning reaction mixture of potassium chlorate and sucrose. The red colour originates from strontium sulphate. The orange/yellow colour originates from sodium chloride. The green colour originates from barium chlorate and the blue colour originates from copper (I) chloride. The lilac colour that should be evident from the potassium chlorate is washed out by the other colours, all of which are more intense (only to be demonstrated by a professionally qualified chemist following a legally satisfactory hazard asessment). Improperly done, this reaction is dangerous!

The picture above shows the colour arising from adding common salt (NaCl) to a burning mixture of potassium chlorate and sucrose.

Cartoon by Nick D Kim (nearingzero.net, used by permission).

Isolation

Isolation: sodium would not normally be made in the laboratory as it is so readily available commercially. All syntheses require an electrolytic step as it is so difficult to add an electron to the poorly electronegative sodium ion Na⁺.

Sodium is present as salt (sodium chloride, NaCl) in huge quantities in underground deposits (salt mines) and seawater and other natural waters. It is easily recovered as a solid by drying.

Sodium chloride has a high melting point (> 800°C) meaning that it sould be expensive to melt it in order to carry out the electrolysis. However a mixture of NaCl (40%) and calcium chloride, CaCl₂ (60%) melts at about 580°C and so much less energy and so expense is required for the electrolysis.

cathode: Na⁺(l) + e^- → Na (l)

anode: Cl^-(l) → ¹/₂Cl₂ (g) + e^-

The electrolysis is carried out as a melt in a "Downs cell". In practice, the electrolysis process produces calcium metal as well but this is solidified in a collection pipe and returned back to the melt.

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Sodium	Sodium
Natrium	Natrium
Sodio	Sodio
Natrium	Sódio