Noble gas
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The noble gases are the members of group 18 of the periodic table: helium, neon, argon, krypton, xenon, radon and, in some cases, oganesson. Under standard conditions, the first six of these elements
Thanks to its characteristic spectral lines, Helium was discovered to exist on the Sun before it was discovered on Earth.
Liquid helium is used to cool superconducting magnets in modern MRI scanners.
Goodyear Blimp
15,000-watt xenon short-arc lamp used in IMAX projectors
Chemical element
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A chemical element is a species of atom defined by its number of protons. The number of protons is called the atomic number of that element. For example, oxygen has an atomic number of 8: each oxygen
Metals (blue) and metalloids (green) in the periodic table
John Dalton's list of atomic weights & symbols, 1808
Estimated distribution of dark matter and dark energy in the universe. Only the fraction of the mass and energy labeled "atoms" is composed of elements.
Robert Boyle, c. 1740