Hello, and welcome to the fifth instalment of the Element of the Month – a regular feature on the Radleys blog. To choose the element of the month, we used a random number generator to produce a figure between 1 and 118 – the current number of elements in the periodic table. This month, we drew the number 11, making sodium our fifth element of the month. Sodium – The Key Facts Sodium is a chemical element with the atomic number 11 and the symbol Na – hence the ever popular joke: “Do you know any sodium jokes? Na.” A soft, silvery white and highly reactive metal, sodium was first isolated in 1807 by Humphry Davy during the process of electrolysis of sodium hydroxide. It’s symbol and name derive from the Latin Natrium or Arabicnatrun and the Egyptian word ntry (Natrun), all of which refer to soda or sodium carbonate. Fascinating Facts about Sodium As a free metal, sodium does not exist in nature and must be prepared from its compounds, which have been used for centuries. Despite this, it comprises of about 2.6% of the Earth’s crust, making it the most abundant alkali metal and the sixth most abundant element on Earth, where it exists in minerals such as rocksalt, feldspars, and sodalite. On top of being highly abundant in the Earth’s crust, sodium and chloride also happen to be the most common dissolved elements (as measured by weight) in the oceans. This is due to the fact that sodium is highly water soluble. Sodium ions have therefore been seeping out of the earth’s minerals for eons. Although shiny and beautiful, sodium tarnishes within a few seconds when it is exposed to the air. It is a highly reactive element: as a pure element sodium has to be kept under oil or kerosene – when exposed to water it ignites. Another explosive fact: the use of sodium in fireworks is what gives them the gold or yellow colour. The colour is so bright that it is not usually used with others because it masks them. Sodium is an essential element for the nutrition of animals, people and some plants, and humans have known this since prehistoric times. In humans, sodium is essential to cellular function for many reasons; to maintain fluid balance in the cells and the rest of the body, and for the absorption of nutrients such as glucose. In fact, sodium is also critical to the function of the human nervous system and to muscular contractions. Although it is a metal, when at room temperature sodium can be cut through with a butter knife! Sodium metal can be used as a heat exchanger in certain nuclear reactors and is generally used in the chemicals industry. Sodium salts and compounds can be put to a multitude of other uses, such as soap making, food preservation, vapour lamps, a desiccant and as a de-icing agent. And that, folks, is sodium, one of the most used and essential elements on Earth. Come back next month, when we’ll be taking a close look at Germanium.