Helium
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Helium is a chemical element; it has symbol He and atomic number 2. It is a colorless, odorless, non-toxic, inert, monatomic gas and the first in the noble gas group in the periodic table. Its boiling
Helium discharge tube
Spectral lines of helium
Sir William Ramsay, the discoverer of terrestrial helium
The cleveite sample from which Ramsay first purified helium
Hydrogen
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Hydrogen is a chemical element; it has the symbol H and atomic number 1. It is the lightest and most abundant chemical element in the universe, constituting about 75% of all normal matter. Under stand
Helium
…it does not have a melting point at standard pressures. It is the second-lightest and second-most abundant element in the observable universe, after hydrogen. It is present at about 24% of the total elemental mass, which is more than 12 times the mass of all the heavier elements combined. Its abundance is…
Purple glow in hydrogen's plasma state.
Robert Boyle, who discovered the reaction between iron filings and dilute acids
Antoine Lavoisier, who identified the element that came to be known as hydrogen
The Hindenburg over New York City in 1937