The Noble Gases On the periodic table, the noble gases are the elements in the last left column. The noble gases are helium (He), neon (Ne), argon (Ar), krypton (Kr), xenon (Xe), and radon (Rn). These are also known as the group O elements. The noble gases got there name because they are extremely unreactive. The name emphasizes the tendency of the elements to exist as separate atoms rather than in combination with other atoms. The original name of the group was rare gases. The earn this name because they occur in the atmosphere in small amounts. Since they rarely combine with other elements, scientist also called them inert gases. HELIUM The first noble gas is helium. Helium comes from the Greek word helios meaning "sun." It is inert, colorless, and odorless. Helium was discovered by the French astronomer Pierre Jansen. He discovered it in the corona of the sun during an eclipse in 1868. After it was discovered, it was named by the British chemist Sir Edward Frankland and the British astronomer Sir Joseph Norman Lockyer. Now scientist knew that helium existed on the sun, but they didn't know if it existed on earth. In 1890, an American chemist, William F. Hillebrand noticed a gas coming from a sample of urainite when he washed it in acid. Hillebrand thought that the gas that found was nitrogen. Sir William Ramsay, a British chemist, disagreed with Hillebrand. Ramsay repeated the experiment using cleveite instead of uraninte. Ramsay found nitrogen, argon and another gas. He sent samples to Sir William Crookes and Sir Norman Lockyer. Lockyer confirmed the samples were helium, and in 1895, investigators were finding helium in the atmosphere. Helium has monatomic molecules and is the second lightest gas. Helium freezes at -272.2 C (-451.9 F) and boils at -268.9 C (-452.0 F). The density of helium is 0.1664 g/liter at 20 C (68 F). The atomic weight of helium is 4.003, and its atomic number is 2. Its single electron shell is filled, making it very hard to react with other elements and the resulting compounds quite unstable. Of all the gases, helium is the most difficult to liquidfy and is impossible to solidify. This property makes liquid helium extremely useful as a refrigerant and for experiments it works in producing and measuring temperatures close to absolute zero. At a temperature slightly above absolute zero, helium can be transformed into helium II. This is also called superfluid helium. Helium II has no freezing point and a viscosity of zero. Helium is the second most abundant element in the known universe. However, it is rare on earth. It is primarily found mixed with natural gas trapped in underground pockets. Once helium is released into the earth's atmosphere it can't be recovered. Helium is the sixth most abundant gas in the earth's atmosphere. Helium occurs in the atmosphere in the proportion of 5.4 parts per million. At higher altitudes, the proportion increases. Helium has five isotopes. The most common isotope of helium is helium-4. Helium probably comes from radioactive alpha emitters in rocks. Helium-3 and helium -5 exists in nature. Helium-6 and -8 are both radioactive isotopes. They decay into lithium-6 and -8. It is possible to obtain pure helium from the atmosphere, but the general procedure to helium is to liquidfy air to a temperature somewhat lower than the temperature of hydrogen. Helium then remains because it has the lowest boiling point. Helium is also extracted form raw natural gas. Helium has many uses. Helium is preferred over hydrogen as the lifting gas in balloons. It has 92% of the lifting power of hydrogen, but it weighs twice as much. It is also used to strengthen and pressurize the structure of rockets and the tanks of fuel. Helium is also used in nuclear reactors because it remains inert and nonreactive. It is used in arc welding for light metals such as aluminum and magnesium. Helium takes the place of nitrogen as part of artificial atmosphere used by deep-sea divers and caisson workers. The artificial atmosphere is also used in medicine. --The largest users of helium are agencies of the Untied States government. NEON The next noble gas is neon, Neon comes from the Greek word neos meaning "new." It is colorless, odorless, and gaseous. Sir William Ramsay and Morris W. Travers were celebrating their other discovery of krypton when the revealed neon. Ramsay thought he found a pattern on the periodic table. He now had a chance of finding something now that he knew what to look for. Ramsay and Travers had looked for a gas and found krypton. What they did not know was that they had also found neon. Neon was being drawn off with helium and argon during an experiments. Since helium and argon had already been found, they knew that a gas existed between them. To find the gas they used a liquid-air machine gun. When they improved the sensitivity of their fractional distillation procedure, they found neon. Neon is located in group 0 or VIIIA (noble gases) and period two. Neon is very stable because their electron orbital are completely filled. The electron configuration of neon is 1s2s2p. However, ionized versions of this atom can combine with a proton, or hydrogen ion, to form a two-element ion. Unlike other gases, neon is monatomic. This means a molecule of neon gas is made of one atom. Out of all the gases in the earth's atmosphere, neon is ranked fifth, and it is the fourth most abundant in the universe. How do we get neon? Neon is produced as a secondary product at liquid-nitrogen/oxygen plants. When nitrogen and oxygen are liquefied, other gases are left. The gases that are leftover are neon, helium, and some hydrogen . The chilled neon is removed by passing it through activated charcoal. In 1912, the first demonstration of the existence of an isotope was performed with neon. Neon has nine isotopes: Ne - Ne. Three of neon's isotopes occur naturally in stable form. Neon-20 is about 90% of neon in the atmosphere; neon-22 makes up about 10%; and neon-21 makes up a little. The other six isotopes of neon are radioactive and artificially produced. Neon is used for its commercial application in neon lights or advertising. When neon is put in a tub and has an electrical pass through it, it emits the light. When the neon tubes are bent their quality of light is not distorted. Like helium, liquid neon is used as a cryogenic refrigerant. However, neon is better because it has over 40 times more refrigerating compacity. ARGON What is the next noble gas? It is argon. Argon comes from the Greek word argos which means "inactive." Sir William Ramsay took a sample of air after removing oxygen and nitrogen. He did this after Rutherford observed air after oxygen was taken out. In addition to the gases, Ramsay took out carbon dioxide, dust, and moisture. After all this a gas was remaining. He thought he was working with a second form of nitrogen. Spectroscope test were done and Ramsay and Crookes found lines not belonging to any known gas. In 1894, Ramsay and a coworker, Lord Rayleigh, found a place for the gas. argon was now discovered. Argon is colorless and odorless. It is also composed of monatomic molecules. It is the third most abundent gas in the atmosphere. It has an atomic weight of 39.948 and atomic number of 18. It is located in group 18 and in period 3. Argon is produced by the fractional distillation of air. It has been considered a byproduct of nitrogen and oxygen production. It is also formed in a process known as electron-capture decay. To form isotopes potassium-40 is converted into argon. Argon has fifteen isotopes with an atomic weights between 32 and 46. How is argon used? It is used to fill electric light bulbs. In light bulbs, it prevents the evaporation of the tungsten filament. It is also used with neon in neon lamps. In the lamps, argon gives off a blue light. Argon is needed in electric-arc technology, lasers, and arc welding. Argon also tells date of things. It can be compared to potassium in rock samples. If the ratio of argon to potassium is larger then the rocks are older. KRYPTON The fourth noble gas in Krypton. Krypton got its name from the word kryptos. Kryptos means "hidden." In 1898, Sir William Ramsay and Morris W. Travers began to look for more gases. At first, they tried to find the gases by heating materials. They could not find any gases so they began using a liquid-air machine. The machine was set up to produce argon. They did the experiment and captured all the residues of liquid helium and argon. After the residues were captured, krypton was discovered. Krypton is a dense, colorless, odorless, and tasteless gas. It has an atomic weight of 83.80 and an atomic number of 36. It is the seventh most abundent gas in the atmosphere and is present in the atmosphere in about 1 part in 20 million by volume. Krypton is not totally inert. Today krypton is combined with fluorine to form krypton fluoride. Today krypton is produced the same way it was discovered. Sometimes xenon is found in krypton, but it is not enough to change or alter it. Krypton has 27 isotopes. They range from atomic weights 72 to 94. Of the radioactive isotopes, none of them are naturally occurring kryptons. Like argon and neon, krypton is used in incandescent bulbs. It can be used with one of the gases or by itself. When electricity passes through krypton, it emits a bright, orange-red color. The lights used on runways because they can be seen at night or in fog. The isotope krypton-85 is used as a source of radiation for the thickness gages and leak-testing instruments. -- The basis for the current definition of a meter is krypton-86, which is 1,650,762.73 of krypton-86. XENON Xenon is the fifth noble gas. It comes from the Greek word, xenos, which means "strange." Who discovered xenon? It was Ramsay and Travers who also discovered neon and krypton. To get xenon, the scientist adjusted the temperatures of gases and when they where finished they would get xenon. The scientist called it the "strange one" because it took nearly a month to find it. Xenon is a heavy gas. It is almost 4.5 times heavier than air. It is also colorless, odorless, and tasteless. Xenon has an atomic number of 54 and an atomic weight of 131.30. It melts at -111.9 C and boils at -107.1 C. It boils between carbon dioxide and oxygen. Xenon is produced by fractional distillation of liquid air. The noble gases are thought to be totally inert. However, in 1962, Neil Bartlett combined xenon with an ion of platinum and fluorine. The first noble gas compound was produced. It has four oxidation states. They are +2, +4, +6, and +8. Xenon has 35 known isotopes. The isotopes have atomic weights between 114 and 142. Xenon -129 , -131, and - 132 most naturally occur. Xenon -133 and -135 are byproducts of neutron radiation. Xenon is used mostly in strobe lights. When xenon is excites it produces a white light. It is also used in nucleur power reactors. RADON The six and final noble gas is radon. Radon was discovered by the German chemist Friedrich Earnest Dorn, in 1900. At the time, he was studying the decay of radium. He was looking at the mass when he noticed that there was a presence of radioactive gas. Dorn called the gas, niton, which means "shining." In 1922 it was given the name radon. Radon is a heavy radioactive gas. It has an atomic number of 86 and an weight of 222. Radon boils at -62 C. At -71 C, radon gas liquefies and changes into its solid state. When it is a solid, it glows a yellow and red-orange depending on the temperature. Radon is not totally inert. The one compound of radon is radonfluoride, RaF. Radon has 29 isotopes. Radon-222 was the type of radon that was actually discovered by Dorn. Radon-222 is the most abundent isotope. It has a half-life of 3.8 days. It is captured by passing air through radium salt. Then it is present when the air and radon are collected. Radon-222 is used to treat tumors. To treat tumors, the gas is placed in a tube which is then inserted into the diseased tissue.