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    He

    Helium

    Noble Gas

    Atomic Number: 2 • Atomic Mass: 4.0026 u • Period: 1 • Group: 18

    Electron Configuration: 1s²
    Phase: Gas
    Electronegativity: 0
    Hydrogen (H)Lithium (Li)
    OverviewPropertiesAtomic StructureOccurrenceApplicationsHistory

    History

    Helium has been known since ancient times

    Historical Timeline

    First detected as an unknown yellow spectral line in sunlight during a solar eclipse in 1868

    Independently discovered by Pierre Janssen and Norman Lockyer

    First isolated on Earth by William Ramsay in 1895

    Found in natural gas deposits in the United States in 1903