Getting to Know the Periodic Table of Elements: Fluorine, Neon, and Sodium
Fluorine
Etymology: From Latin and French fluere: flow or flux)
What it is: Fluorine is the most electronegative and reactive of all elements. It is a corrosive gas, which reacts with most organic and inorganic substances. Finely divided metals, glass, ceramics, carbon, and even water burn in fluorine with a bright flame.
How and when it was first isolated: Known in 1529, the element was only isolated in 1866.
Why it is important to your teeth: In very small amounts fluoride helps prevent dental cavities. However, the presence of fluorine in drinking water to the extent of 2 ppm may cause mottled tooth enamel in children acquiring their permanent teeth.
Good for your teeth but...: Elemental fluorine and the fluoride ion are highly toxic. The recommended maximum allowable concentration for a daily 8-hour time-weighted exposure is 1 ppm. And? Elemental fluorine has been studied as a rocket propellant.
Atomic Number: 9
Atomic Symbol: F
Atomic Mass: 19
Neon
Etymology: From the Greek neos: new
What it is: Discovered in 1898. Neon is a rare gaseous element present in the atmosphere to the extent of 1 part in 65,000 of air. It is obtained by liquefaction of air and separated from the other gases by fractional distillation. In a vacuum discharge tube, neon glows reddish orange. Of all the rare gases, the discharge of neon is the most intense at ordinary voltages and currents.
What it is used for: Although neon advertising signs account for the bulk of its use, neon also functions in high-voltage indicators, lightning arrestors, wave meter tubes, and TV tubes. Neon and helium are used in making gas lasers.
Why it makes a good refrigerant: It has over 40 times more refrigerating capacity per unit volume than liquid helium and more than three times that of liquid hydrogen. It is compact, inert, and is less expensive than helium when it meets refrigeration requirements.
Atomic Number: 10
Atomic Symbol: Ne
Atomic Mass: ~20
Sodium
Etymology: English, soda; Medieval Latin, sodanum: a headache remedy
What it is: Long recognized in compounds, sodium was first isolated in 1807 by electrolysis of caustic soda.
How it is obtained: Sodium is present in fair abundance in the sun and stars. The D lines of sodium are among the most prominent in the solar spectrum. Sodium is the fourth most abundant element on Earth, comprising about 2.6% of the Earth's crust; it is the most abundant of the alkali group of metals. It is now obtained commercially by the electrolysis of absolutely dry fused sodium chloride. This method is much cheaper than that of electrolyzing sodium hydroxide, as was used several years ago.
Please pass the salt: The most common compound is sodium chloride (table salt), but it occurs in many other minerals, such as soda niter, cryolite, amphibole, zeolite, etc. Beginning thousands of years ago and until about 200 years ago, salt was taxed, used as a form of currency, and the cause of more than one battle. Roman legionnaires were paid in salt - a salarium (hence, the word salary).
Atomic Number: 11
Atomic Symbol: Na
Atomic Mass: ~23
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