Sunday, October 14, 2012

Sodium (natrium) - not just salt

Structure of sodium chloride,
"showing octahedral coordination around Na+ and Cl- centres.
This framework disintegrates upon dissolution in water
and reassembles upon evaporation"
"Sodium is a chemical element with the symbol Na (from Latin: natrium) in the periodic table and atomic number 11.

It is a soft, silvery-white, highly reactive metal and is a member of the alkali metals. 20 isotopes are known but only 23Na is stable.

Many sodium compounds are useful for humans, such as sodium hydroxide (lye) for soap making, and sodium chloride for use as a deicing agent and a nutrient (edible salt).

Salt as salary and Medieval aspirin
Salt has been an important commodity in human activities, as shown by the English word salary, which derives from salarium, the wafers of salt sometimes given to Roman soldiers along with their other wages.

In medieval Europe, a compound of sodium with the Latin name of sodanum was used as a headache remedy. The name sodium is thought to originate from the Arabic suda, meaning headache, as the headache-alleviating properties of sodium carbonate or soda were well known in early times

Sodium is created in stars
23Na is created in the carbon-burning process by fusing two carbon atoms together; this requires temperatures above 600 megakelvins and a star with at least three solar masses.

When sodium or its compounds are introduced into a flame, they turn it yellow, because the excited 3s electrons of sodium emit a photon when they fall from 3p to 3s; the wavelength of this photon corresponds to the D line at 589.3 nm. Spin-orbit interactions involving the electron in the 3p orbital split the D line into two; hyperfine structures involving both orbitals cause many more lines.

In the interstellar medium, sodium is identified by the D line; though it has a high vaporization temperature, its abundance allowed it to be detected by Mariner 10 in Mercury's atmosphere.

Oceans are salty
Many salts of sodium are highly water-soluble, and their sodium has been leached by the action of water so that chloride and sodium are the most common dissolved elements by weight in the Earth's bodies of oceanic water.

Sodium in the crust of planet Earth
Sodium is the sixth most abundant element in the Earth's crust , and exists in numerous minerals such as feldspars, sodalite and rock salt.

Because of its high reactivity the free metal does not occur in nature, but instead must be prepared from its compounds; it was first isolated by Humphry Davy in 1807 by the electrolysis of sodium hydroxide.

Sodium and living beings

Sodium is an essential element for all animals and some plants.

In animals, sodium ions are used against potassium ions to build up charges on cell membranes, allowing transmission of nerve impulses when the charge is dissipated.

The consequent need of animals for sodium causes it to be classified as a dietary inorganic macro-mineral."

[Selections copied from the article are rearranged by me]
Read the entire article from wikipedia

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