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atomic number of helium, noble gases, alpha particles, periodic table, protons

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Helium, symbol He, colorless, odorless chemical element that occurs as a gas at room temperature. The atomic number of helium is 2, with two protons in its nucleus. The element is listed in group 18 (or VIIIa) of the periodic table. Helium is one of the noble gases and is almost chemically inert. Helium is the second most abundant element in the universe, after hydrogen. The name comes from the Greek word helios, meaning “Sun.”

The French astronomer Pierre Janssen discovered helium in the spectrum of the corona of the Sun during an eclipse in 1868. Shortly afterward it was identified as an element and named by the British chemist Sir Edward Frankland and the British astronomer Sir Joseph Norman Lockyer. The gas was first isolated from terrestrial sources in 1895 by the British chemist Sir William Ramsay, who discovered it in cleveite, a uranium-bearing mineral. In 1907 the British physicist Sir Ernest Rutherford showed that alpha particles are the nuclei of helium atoms, which later investigation confirmed.

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atomic number of helium, noble gases, alpha particles, periodic table, protons, nucleus, corona, hydrogen, eclipse, room temperature, spectrum, universe, element, symbol, Sun, investigation, gas, group

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