Sodium

Sodium (symbol Na, from the Latin name natrium) is the chemical element number 11 in the periodic table of elements. It follows that its nucleus includes 11 protons, and 11 electrons orbit around it (according to the simplified model known as "Niels Bohr atom"). Even if many isotopes can be artificially made, all decay in a short time. As a result, all sodium found in nature (mainly in sea water) has the composition ₁₁Na²³, meaning that the nucleus includes 12 neutrons. The atomic mass of sodium is 22.9898; if it is rounded, it would be 23.

Sodium,  ₁₁Na

General properties
Appearance	silvery white metallic
Standard atomic weight (Ar, standard)	22.98976928(2)
Sodium in the periodic table
Hydrogen Helium Lithium Beryllium Boron Carbon Nitrogen Oxygen Fluorine Neon Sodium Magnesium Aluminium Silicon Phosphorus Sulfur Chlorine Argon Potassium Calcium Scandium Titanium Vanadium Chromium Manganese Iron Cobalt Nickel Copper Zinc Gallium Germanium Arsenic Selenium Bromine Krypton Rubidium Strontium Yttrium Zirconium Niobium Molybdenum Technetium Ruthenium Rhodium Palladium Silver Cadmium Indium Tin Antimony Tellurium Iodine Xenon Caesium Barium Lanthanum Cerium Praseodymium Neodymium Promethium Samarium Europium Gadolinium Terbium Dysprosium Holmium Erbium Thulium Ytterbium Lutetium Hafnium Tantalum Tungsten Rhenium Osmium Iridium Platinum Gold Mercury (element) Thallium Lead Bismuth Polonium Astatine Radon Francium Radium Actinium Thorium Protactinium Uranium Neptunium Plutonium Americium Curium Berkelium Californium Einsteinium Fermium Mendelevium Nobelium Lawrencium Rutherfordium Dubnium Seaborgium Bohrium Hassium Meitnerium Darmstadtium Roentgenium Copernicium Nihonium Flerovium Moscovium Livermorium Tennessine Oganesson Li ↑ Na ↓ K neon ← sodium → magnesium
Atomic number (Z)	11
Group	group 1 (alkali metals)
Period	period 3
Block	s-block
Element category	alkali metal
Electron configuration	[Ne] 3s1
Electrons per shell	2, 8, 1
Physical properties
Phase at STP	solid
Melting point	370.944 K ​(97.794 °C, ​208.029 °F)
Boiling point	1156.090 K ​(882.940 °C, ​1621.292 °F)
Density (near r.t.)	0.968 g/cm3
when liquid (at m.p.)	0.927 g/cm3
Critical point	2573 K, 35 MPa (extrapolated)
Heat of fusion	2.60 kJ/mol
Heat of vaporization	97.42 kJ/mol
Molar heat capacity	28.230 J/(mol·K)
Vapor pressure P (Pa) 1 10 100 1 k 10 k 100 k at T (K) 554 617 697 802 946 1153
Atomic properties
Oxidation states	−1, +1 (a strongly basic oxide)
Electronegativity	Pauling scale: 0.93
Ionization energies	1st: 495.8 kJ/mol 2nd: 4562 kJ/mol 3rd: 6910.3 kJ/mol (more)
Atomic radius	empirical: 186 pm
Covalent radius	166±9 pm
Van der Waals radius	227 pm
Spectral lines of sodium
Other properties
Natural occurrence	primordial
Crystal structure	​body-centered cubic (bcc)
Speed of sound thin rod	3200 m/s (at 20 °C)
Thermal expansion	71 µm/(m·K) (at 25 °C)
Thermal conductivity	142 W/(m·K)
Electrical resistivity	47.7 nΩ·m (at 20 °C)
Magnetic ordering	paramagnetic
Magnetic susceptibility	+16.0·10−6 cm3/mol (298 K)
Young's modulus	10 GPa
Shear modulus	3.3 GPa
Bulk modulus	6.3 GPa
Mohs hardness	0.5
Brinell hardness	0.69 MPa
CAS Number	7440-23-5
History
Discovery and first isolation	Humphry Davy (1807)
Main isotopes of sodium
Iso­tope Abun­dance Half-life (t1/2) Decay mode Pro­duct 22Na trace 2.602 y β+ 22Ne 23Na 100% stable 24Na trace 14.96 h β− 24Mg

Sodium pellets in a container

Contents

Properties

Sodium is a light, silver-coloured metal. Sodium is so soft that it can be easily cut with a knife. When it is cut, the surface will become white over time. This is because it reacts with air to form sodium hydroxide and sodium carbonate. Sodium is a little lighter than water; when it reacts with water it floats. This reaction is very fast. Hydrogen and sodium hydroxide are produced. The hydrogen may ignite. Since sodium melts at a low temperature, it melts when it reacts with water. It has one valence electron which is removed easily, making it highly reactive.

Compared with other alkali metals (metals in the first column of the periodic table), sodium is usually less reactive than potassium and more reactive than lithium.

Chemical compounds

These are chemical compounds that contain sodium ions. Sodium only exists in 1 oxidation state: +1.

• Sodium aluminum fluoride, used to make aluminum
• Sodium amide, very strong base
• Sodium arsenite, colorless solid, very toxic
• Sodium arsenate, oxidizing agent, very toxic
• Sodium azide, used in airbags
• Sodium bicarbonate, baking soda, used in cooking
• Sodium bismuthate, oxidizing agent, used to test for manganese
• Sodium bisulfate, acidic, used to increase pH
• Sodium bromate, oxidizing agent, used to dye hair
• Sodium bromide, rare, used in some medicine
• Sodium carbonate, used to make glass
• Sodium chlorate, used in some explosives
• Sodium chlorite, used in disinfectants
• Sodium chloride, table salt
• Sodium chromate, yellow, oxidizing agent, toxic
• Sodium dichromate, orange, oxidizing agent, toxic
• Sodium fluoride, used in toothpastes, bitter, toxic in large doses
• Sodium hydroxide, lye, used in soap, strong base
• Sodium hypochlorite, bleach, disinfectant
• Sodium hypophosphite, reducing agent, poisonous
• Sodium iodate, oxidizing agent, prevents iodine deficiency
• Sodium iodide, weak reducing agent, prevents iodine deficiency
• Sodium manganate, rare green solid
• Sodium nitrate, used in blasting powder
• Sodium nitrite, used in food preservation
• Sodium periodate, oxidizing agent
• Sodium permanganate, less common than potassium permanganate, oxidizing agent
• Sodium phosphate, various uses
• Sodium phosphide, catalyst
• Sodium phosphite, toxic, reducing agent
• Sodium selenate, strong oxidizing agent, other selenium compounds
• Sodium selenide, strong reducing agent, reactive
• Sodium selenite, weak oxidizing agent, vitamin supplement
• Sodium sulfate, bitter, laxative
• Sodium sulfite, weak reducing agent, used to preserve dried food
• Sodium tellurate, strong oxidizing agent
• Sodium telluride, strong reducing agent, reacts with air easily
• Sodium tellurite, main tellurite compound

Discovery and name

Sodium was discovered by Sir Humphrey Davy, an English scientist, back in 1807. He made it by the electrolysis of sodium hydroxide. It is named after soda, a name for sodium hydroxide or sodium carbonate.

Use as element

It is used in the preparation of organic compounds. It is also used in the street lights that are orange, and ultra violet lights.

Use as compounds

Sodium compounds are used in soaps, toothpaste, baking and antiacids. .

Occurrence and production

Sodium does not exist as an element in nature; its easily removed valence electron is too reactive. It exists as an ion in chemical compounds. Sodium ions are found in the ocean. It is also found as sodium chloride in the earth's crust, where it is mined.

Sodium is normally made by electrolysis of very hot sodium chloride that was melted.

Use in organisms

Sodium ion in the form of sodium chloride is needed in the human body, but large amounts of it cause problems, which is why one should not eat too much salt and other food items with huge sodium amount (such as biscuits with baking soda). Many organisms in the ocean depend on the proper concentration of ions in sea water to live.

Related pages

• List of common elements
• Hyponatremia (a medical problem caused by not having enough sodium in the body)