Shiny gray metal which quickly oxidizes upon exposure to the atmosphere to form a pale gray oxide m.p. 97.81 ºC; 208.06 ºF b.p. 882.9 ºC; 1621.2 ºF density 0.971 g/cc; 60.618 pounds/cubic foot	memory peg
	1807 Sir Humphry Davy, England
	Neter = soda (Hebrew) named Sodium by the discoverer, and Natrium by Jakob Berzelius in 1813

Soda (Sodium carbonate, Na₂CO₃) from the Egyptian salt lakes, and Potash (Potassium carbonate, K₂CO₃), obtained from the ashes of plant material, were known since Antiquity and used for washing. There was made no difference between both substances, which were named by the Israelites neter, by the Greek νιτρον (nitron) and by the Romans nitrum (cf. Nitrogen). Derived from these is the word natron, the name used by the European alchemists for potash and soda. In Arab, the same substances were named alkali (see Potassium / Kalium.) The name soda is a derivation from "sodanum", a Neolatin name for a headache remedy. This word is derived from Arabic Sudâ (soda). The modern spelling of the element in Arabic uses the emphatic S (shown uppercase in transliteration) from the original Arabic word.

The difference between both substances was recognized by Andreas Sigismund Marggraf (1709-1782) in 1758, among other he described the different colorations potash and soda produce in flame. In his "Démonstration de la possibilité de tirer les sels alcalis fixes du tartre, par le moyen des acides, sans employer l'action d'un feu véhément" (note) he named them alcali minerale (mineral alkali or soda) and alcali vegetabile (vegetable alkali or potash). These names were not generally accepted, and chemists used soda and potash for both substances. Not satisfied with these names, Martin Heinrich Klaproth, suggested in his paper for the Royal Academy of Berlin of 26 January 1797, the name kali for potash and natron for soda (note):

(translation: The word potash, in the new chemical nomenclature upgraded to a generic name, can not claim general acceptance in Germany, since it has only a bad etymological value and merely finds its origin in the fact that in former years for burning out the condensed lye of wood ashes an iron pot (lower saxon Pott) was used in stead of the modern calcination oven.
My proposal is: to determine the name Kali instead of the present names vegetable alkali, vegetable lye salt, potash etc.; and to return to its old name Natron instead of the names mineral alkali, soda etc.).

Gay-Lussac and Thénard, who too investigated the alkalis, named the metals initially métal de potasse and métal de soude, and later also Potassium and Sodium.

The results of Davy's research were made public in German by Ludwig Wilhelm Gilbert in his Annalen der Physik of 1809 (vol. 31). Many articles were translated by Gilbert himself, he calls his work a "free translation" since he added his own comments. I have not seen Gilbert's translation of Davy's article yet, since vol. 31 (vol. 1 of the new series) is not available in the Bibliotheca Gallica (it would be interesting to see how Gilbert translated the naming paragraph quoted above). However, a note in a translation of a later article by Davy (note) makes clear what Gilbert's idea of a translation was:

Translation: The reader will remember from these Annalen that Davy named these bodies Potassium, which I replaced by Kalium, just as Davy's name for the Natron-Metal, Sodium, is represented by Natronium, in agreement with the German nomenclature. These names I will use throughout this article.

Gilbert obviously followed the 1797 proposal by Klaproth.
In 1808 Gehlen suggested Kalin(um) and Natrin or Natrinmetall.

In 1813 Berzelius published in a British journal, Thomas Thomson's Annals of Philosophy, his system of atomic symbols as one- or two-letter abbreviations of Latin names for the elements. In this first paper he followed the British discoverer Davy nomenclature and abbreviated Potassium and Sodium as Po and So. But within a year Berzelius decided in favor of Kalium and Natrium (he seems to be the first to use this shortened form of Natronium).

Despite this, as the list of names in different languages to the left shows, the English and French speaking countries followed Davy and Gay-Lussac/Thénard with Sodium and Potassium, and the Germanic countries adopted Gilbert/Klaproth's names Natrium and Kalium.

The following explanation comes from Egyptian loan-words in English:

12*) natron
Derives via French and Spanish from Arabic natrun or nitrun, which derives from Greek nitron (= "soda") (e.g. Herodotus II, 86-87, where the form litron occures). The Greek derives with certainty from AE nTrj or nTry.t (netjeri). The Egyptians distinguished between nTrj Sm' ("southern natron"), stemming from el-Kab, and nTrj mHw ("northern natron"), stemming from Wadi Natrun (HWB p.445). The Egyptian word was also borrowed into Akkadian (nit(i)ru) and Hebrew (neter, cf. Jer. 2:22, used for washing). The element Natrium (symbol: Na) derives its name from natron; alternative name in English: Sodium, from soda. Natron is a natural mixture of sodium carbonate and sodium bicarbonate (McGready). Niter is potassium nitrate (KNO₃), also called saltpeter, but originally the word was used as equivalent for natron.

At room temperature sodium is soft and can be cut with a knife. Exposed to humid air, the silver white surface quickly oxydizes.

• Mary Elvira Weeks, Discovery of the Elements, comp. rev. by Heny M. Leicester (Easton, Pa.: Journal of Chemical Education, 1968), pp. 433-457.
• Natrium. Gmelins Handbuch der anorganische Chemie, 8. Aufl.; System-Nummer 21 (1928).