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Explore the updated online encyclopedia from Encyclopaedia Britannica with hundreds of thousands of articles, biographies, videos, images, and Web sites.
Explore the fact-checked online encyclopedia from Encyclopaedia Britannica with hundreds of thousands of objective articles, biographies, videos, and images from experts.
Helium: Helium (He), chemical element, inert gas of Group 18 (noble gases) of the periodic table. The second lightest element (only hydrogen is lighter), helium is a colourless,...