Occurrence of Group 18 Elements
Group 18 elements are called as the noble gases or inert gases due to completely filled valence shells which makes them highly stable. They occupy the last column of the periodic table. Group 18 of the periodic table consists of six elements:
The existence of helium was first claimed in the year 1868. Radioactive elements were used to establish the existence of this element. It is found in the atmosphere and in earth’s crust in small quantities.
Noble Gases – Group 18 Elements
Argon, the second member of group 18 elements, gets its name from a Greek word which means inert representing the chemical nature of argon. Argon found in nature makes up to 0.947% of dry air. It is the most abundant noble gas found in dry air. The concentration of argon above the sea level is slightly more. The solubility of argon in water is more than nitrogen which makes it available in sea and river water. This is the reason behind the presence of argon gas in the gas-bladder of fishes. It is found in the free state in plants and blood cells of animals.
Neon was discovered by Morris W.Travers and Sir William Ramsay in the year 1898. This noble gas is widely distributed in the universe and it is the fifth most abundant element in the universe. Neon can be created at high temperatures by thermonuclear reaction between oxygen and carbon which occurs in star cores. Many stars have stable isotopes of neon due to this reaction.
Krypton was discovered by Sir William Ramsay and Morris Travers in the year 1898. In earth’s atmosphere, the concentration of Krypton is observed to be around 1ppm. Krypton is a colourless, odourless and tasteless gas which is often used in fluorescent lamps in combination with other rare gases. The percentage of krypton in space depends on meteoric activities and solar winds.
Xenon is the second last member of group 18 of the modern periodic table having the atomic number of 54. In the earth’s atmosphere xenon is found in traces. Some mineral springs emit xenon. Commercially it is obtained as a by-product of separation of air into oxygen and nitrogen. It has 8 naturally occurring stable isotopes and more than 40 unstable isotopes that undergo radioactive decay. The atmosphere of planet Jupiter contains xenon in high quantity.
Radon was discovered by Friedrich Ernst Dorn in the year 1900. Its atomic number is 86 and has a symbol Rn. Radon is found in uranium rocks, phosphate rocks, metamorphic and igneous rocks due to the radioactive decay of radium-226. Industrially radon is obtained as a by-product the processing of uraniferous ores.
The properties of group 18 elements are still under study and new developments have revealed great information about these gases and their application. Get in touch with the mentor support team at BYJU’S for any further query about group 18 elements.