Helium

helium Helium (Greek helios," sun"), symbol He, inert, colorless, odorless ruffle element. In group 18 of the periodic table, atomic list 2 is integrity of the noble gases. The atomic number of helium is 2. Pierre Janssen observed helium in the spectrum of the corona of the sun during an eclipse in 1868. Shortly after it was identified as an element and named by the apothecary Sir Edward Frankland and the British astronomer Sir Joseph Norman Lockyer. The gas was offset printing isolated from terrestrial sources in 1895 by the British chemist Sir William Ramsay, who discovered it in cleveite. In 1907 Sir Ernest Rutherford showed that alpha particles are the nuclei of helium atoms.

II PROPERTIES AND OCCURRENCE Helium has monatomic molecules, and is the lightest of all gases demur hydrogen. Helium solidifies at -272.2° C; helium boils at -268.9° C. The atomic weight of helium is 4.0026. Helium, standardized the other noble gases, is chemically inert. Its single electron tap out is ...If you want to get a full essay, order it on our website: BestEssayCheap.com

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