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 a large number of 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.

neon ← Sodium → magnesium Li ↑ Na ↓ K 11Na Periodic table
Appearance
silvery white metallic Spectral lines of sodium
General properties
Name, symbol, number	Sodium, Na, 11
Pronunciation	/ˈsoʊdiəm/ SOH-dee-əm
Element category	alkali metal
Group, period, block	1, 3, s
Standard atomic weight	22.98976928(2) g/mol
Electron configuration	[Ne] 3s1
Electrons per shell	2,8,1 (Image)
Physical properties
Phase	solid
Density (near r.t.)	0.968 g/cm3
Liquid density at m.p.	0.927 g/cm3
Melting point	370.87 K, 97.72 °C, 207.9 °F
Boiling point	1156 K, 883 °C, 1621 °F
Critical point	(extrapolated) 2573 K, 35 MPa
Heat of fusion	2.60 kJ/mol
Heat of vaporization	97.42 kJ/mol
Specific heat capacity	(25 °C) 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 (strongly basic oxide)
Electronegativity	0.93 (Pauling scale)
Ionization energies	1st: 495.8 kJ/mol
	2nd: 4562 kJ/mol
	3rd: 6910.3 kJ/mol
Atomic radius	186 pm
Covalent radius	166±9 pm
Van der Waals radius	227 pm
Miscellanea
Crystal structure	body-centered cubic
Magnetic ordering	paramagnetic
Electrical resistivity	(20 °C) 47.7 nΩ·m
Thermal conductivity	(300 K) 142 W/(m·K)
Thermal expansion	(25 °C) 71 µm/(m·K)
Speed of sound (thin rod)	(20 °C) 3200 m/s
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 registry number	7440-23-5
Most stable isotopes
Main article: Isotopes of Sodium
iso NA half-life DM DE (MeV) DP 22Na trace 2.602 y β+→γ 0.5454 22Ne* 1.27453(2) 22Ne ε→γ - 22Ne* 1.27453(2) 22Ne β+ 1.8200 22Ne 23Na 100% 23Na is stable with 12 neutrons

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)