Sodium (Na)

Stable Isotopes of Sodium

Isotope Z(p) N(n) Atomic Mass Natural Abundance Nuclear Spin
Na-23 11 12 22.9897697 100.00% 3/2+


Sodium was discovered in 1807 by Sir Humphry Davy. Its name originates from the English word soda, and its symbol (Na) comes from the Latin word natrium, which refers to the Egyptian word natron, a natural mineral salt primarily made of hydrated sodium carbonate. Other origins may include the Arabic word suda, meaning “headache,” as the headache-alleviating properties of sodium carbonate were well known in early times. Even the English word “salary” derives from the Latin salarium, referring to the wafers of salt sometimes given to Roman soldiers along with their other wages.

Sodium is a soft, bright, silvery metal. It is malleable and can be cut readily with a knife or extruded as wire. In an inert atmosphere it appears like mercury with a blue vapor, and it appears brilliant green at high temperatures, imparting a golden-yellow color to flames. It ignites in air when heated to 120 ºC, burning with a yellow flame and forming a dense white smoke with an acrid color. It also reacts violently with water and is soluble in liquid ammonia, forming a deep blue solution.

Alloys can be formed by combining sodium with a number of metals, including lead, chromium, mercury, aluminum, silicon and iron. The sodium-lead alloy is used commercially to produce tetraethyllead, which has been used historically as an additive to gasoline. Sodium vapor lamps are often used for street lighting in cities, giving colors ranging from yellow-orange to peach as the vapor pressure increases. Major applications of sodium use its compound forms. Millions of tons of sodium chloride, hydroxide and carbonate are produced annually.

Properties of Sodium

Name Sodium
Symbol Na
Atomic number 11
Atomic weight 22.989770
Standard state Solid at 298 °K
CAS Registry ID 7440-23-5 
Group in periodic table
Group name Alkali metal 
Period in periodic table
Block in periodic table s-block 
Color Silvery white
Classification Metallic 
Melting point 97.81 °C
Boiling point 882.9 °C
Thermal conductivity 1.42 W/(m·K) at 298.2 °K
Electrical resistivity 4.2 µΩ·cm at 0 °C
Electronegativity 0.9 
Specific heat 1.21 kJ/kg K
Heat of vaporization 97.7 kJ·mol-1
Heat of fusion 2.6 kJ·mol-1
Density of solid 0.97 g/cm3
Electron configuration [Ne]3s1 
Oxidation state +1
Atomic radius  1.85 Å
Ionic radius Na+: 1.02 Å (coordination number 6) 
Ionization potential 5.139 eV 

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