【導(dǎo)讀】deuterium(D),andoneradioactive,tritium(T).Infact,Ican'timagine

　　

【正文】 things that I found odd when I first learned about potassium was its chemical symbol, so I thought I would see if he felt the same way. But when I asked him if he also found it odd that potassium39。s symbol was K, he blew his wise chemical facade. K? he responded, asserting that the symbol was without a doubt P. Needless to say, we spent a good bit of time arguing whether K or P was the correct symbol. He just wasn39。t buying that the K came from potassium39。s Latin name, kalium, or that I was a chemistry major who knew my elements. I even went as far as looking through my friend39。s apartment for a book that had a periodic table in it, but unfortunately she didn39。t have any science books around. Days later, I caught up with him at the library and was able to show him a copy of the periodic table, thus proving K was really the correct symbol. Looking back, my excitement over talking chemistry at a college outing was a bit nerdy, but this guy didn39。t seem to mind. Although things didn39。t pan out between us, we had chemistry working for us for at least one evening. I just hope that he still remembers the correct symbol for potassium as well as I remember his pickup line. Susan Morrissey received her . in chemistry from Texas Aamp。M University. She is an associate editor covering government and policy issues for Camp。EN. POTASSIUM AT A GLANCE Name: From the English potash. The symbol for potassium es from the Latinkalium,alkali. Atomic mass: . History: Isolated in 1807 by Sir Humphry Davy. Occurrence: The seventh most abundant metal, but it is never found free in nature. Potassium is an essential constituent for plant growth and is found in most soils. It occurs in many minerals mined in Germany, Spain, Canada, the ., and Italy. Appearance: Soft, silvery metal. Behavior: One of the most reactive and electropositive metals. Apart from lithium, it is the least dense metal known. Potassium oxidizes very rapidly in air and must be stored under argon or under a suitable mineral oil. It reacts with water to form potassium hydroxide, hydrogen gas, and heat, and the heat usually ignites the hydrogen. Potassium and its salts impart a lilac color to flames. Uses: The metal is rarely used, but its pounds are important ponents of fertilizers, match heads, glass, soaps, and detergents. The potassium40 isotope is used to date rocks. 11 RUBIDIUM STEPHEN K. RITTER, Camp。EN WASHINGTON Rubidium has the most pleasantsounding name of all the elements, at least in my opinion. It leaves a warm and satisfying feeling when you say it, like the feeling one gets when tasting a good merlot. I39。m not sure that any other element name es close, except maybe beryllium. But honestly, rubidium is not one of the more popular or wellknown elements. The word rubidium es from the Latin rubidus, meaning dark red, which coincidentally is the same color as merlot. The name stems from the color of the two prominent lines in the red region of the element39。s spectrum. Rubidium has a rich chemistry, although most of it is the same as lithium, sodium, and potassium. So in descending order, that makes rubidium fourth place among the alkali metals. And, as in the Olympics, no one remembers who finishes in fourth place. Maybe there is a connection here as to why people usually stop at potassium when they make their way down the first column of the periodic table. Actually, the real reason rubidium39。s popularity suffers is that the element has no known major biological or mineral roles and few mercial applications. This is related to its occurrence in Earth39。s continental crust. Rubidium was originally thought to be rare, but actually it39。s the 22nd most abundant element. At 90 ppm in the crust, this places it, impressively, just after chromium at 102 ppm and ahead of nickel at 84 ppm. For further parison, copper es in at only 60 ppm. The drawback to this claim to fame is that rubidium isn39。t found in large quantities in any one spot. The richest sources of rubidium are a few aluminum silicate minerals, where the element typically is found with cesium and potassium. Rubidium salts also are found dissolved in mineral water. One disappointment is that, despite having a similar Latin root, rubidium is not part of the chemical makeup of a ruby. Ruby, a type of corundum, is an aluminum oxide doped with chromium. To accentuate the positive, there are some interesting things to say about rubidium. For example, one exciting fact about the element is that it39。s easily excitable. The large atomic radius of 248 pm and shielding from the nucleus by innershell electrons means that rubidium39。s 5s electron is barely being held in place. Rubidium39。s first ionization enthalpy of 403 kJ per mol is second only to 376 kJ per mol for cesium. Thus, rubidium and cesium are two of the most reactive elements. Rubidium is a silvery white metal that, unlike Mamp。M candies that melt in your mouth, not in your hand, will start to melt in your hand ( 186。C) and explode in your mouth. Rubidium bursts into flame in air to form a set of oxides and reacts vigorously with water to TIMEKEEPER The tiny timestandard cell from the heart of a rubidium atomic clock. 12 form RbOH, one of the strongest known bases. It has two natural isotopes, 85Rb (%) and 87Rb (%). The latter isotope is radioactive, with a long halflife of 3 1010 years. As for applications, rubidium is used in a few electronic devices, as a frequency reference in atomic clocks, and to estimate the age of rocks. The element39。s future is full of potential if it could be more easily isolated. For example, rubidium pounds are being studied for medical uses, such as a potential antidepressant akin to lithium. A rubidium ionic crystal, RbAg4I5, has high roomtemperature conductivity and could be used in thin films for