Noble Gases: The seven elements that are present in Group 18 of the periodic table are called noble gases. These elements have similar chemical properties show under specific conditions. These elements include Helium, Xenon, Radon, Neon, Argon, Krypton, and Oganesson.
First six elements exist naturally. Radon and Oganesson are radioactive. Oganesson is a man-made element. It is considered to be a noble gas as well as to break the trend. These all elements are colourless, odourless, tasteless, monoatomic, and non-flammable. They are present at the right end of the periodic table. They are also called inert gases because their valence shells are filled.
The abundances of the noble gases decrease with the increase in atomic number. Helium is the most common element in the universe after hydrogen. Noble gases are present in the earth’s atmosphere except helium and radon. These elements are obtained by liquefaction and fractional distillation of air. Helium can be obtained from natural gas. Radom is obtained from the decay of radium. Oganesson is synthesized by striking a target with accelerated particles.
History of noble gases
In 1898, Hugo Erdmann first used the term Noble gas to indicate un-reactivity. In 1784, the English chemist and physicist Henry Cavendish determined that air contains a small proportion of a substance (less than 1%) less reactive than nitrogen.
He indicated these substances by chemically removing all oxygen and nitrogen from a container of air. The nitrogen was oxidized to nitrogen dioxide by electric discharges.
Then it was absorbed by a NaOH solution. The remaining oxygen was removed from the mixture of air with an absorber. The experiment showed that 1/120 of the gas volume remain un-reacted in the container.
In 1868, Pierre Janssen and Joseph Norman Lockyer found the new element in periodic table while looking at the chromosphere of the sun. They found its spectrum as a bright yellow line with a wavelength of 587.49nm.
They assumed it was a sodium line. Helium was identified by a British physicist William Crookes. During a search on argon, William Ramsay isolated helium by heating a mineral cleveite. The newly discovered element was named helium from the Greek word helios.
In 1895, a British Physicist Lord Rayleigh found that samples of nitrogen from the air had a different density than nitrogen obtained from the chemical reaction.
Then along with Scottish chemist William Ramsay discovered the new element argon by modifying the experiment of Cavendish. The newly discovered element was named argon from the Greek word Argos meaning idle. After this discovery, they realized that a class of gases was missing from the periodic table.
Krypton, Neon, and Xenon
William Ramsay continued his search for the discovery of these gases. In 1898, he discovered these elements by chilling a sample of the air to a liquid phase, warming the liquid, and capturing the gases as they boiled off.
Krypton, neon, and xenon were named after the Greek words kryptós (meaning hidden), néos (meaning new), and ksénos (meaning stranger).
Pierre & Curie have discovered that the gas emitted by RD of radioactive In 1899. In 1900, Friedrich Ernst Dorn performed some experiments. He found that RD compounds a radioactive gas.
He named the gas radium emanation (Ra Em). Several names were suggested for this radioactive gas. In 1909, William & Whytlaw-Gray isolated RD and determined it as the heaviest gas. In 1923, the International Union of Pure and Applied Chemistry (IUPAC) named the element radon.
Oganesson is a synthetic element. It was first prepared by a joint team of Russian and American scientists in 2002 at JINR in Russia. In 2015, it was recognized as one of four new elements by the IUPAC and IUPAP. In November 2016, it was named formally. The name was given in the honor of a nuclear physicist Yuri Oganessian.