1
Lightest chemical element; most abundant in the universe as gas.
2
Noble gas; second most abundant in the universe; inert.
3
Basis of organic life; essential for all known compounds.
4
Gaseous element making up about three-quarters of Earth's air.
5
Essential for most combustion and respiration; abundant in air.
6
Noble gas used in bright glass tubes and signs.
7
Reactive alkali metal; key electrolyte in living organisms.
8
Light alkaline-earth metal important for bones and enzymes.
2
7
8
4
3
1
6