Name: hydrogen
Symbol: H
Atomic number: 1
Atomic weight: 1.00794 (7) g m r
Group in periodic table: 1
Group name:
Period in periodic table: 1
Block in periodic table: s-block
CAS registry ID: 1333-74-0
Hydrogen is the lightest element. It is by far the most abundant element in the universe and makes up about about 90% of the universe by weight. Hydrogen as water (H2O) is absolutely essential to life and it is present in all organic compounds. Hydrogen gas was used in lighter-than-air balloons for transport but is far too dangerous because of the fire risk (Hindenburg).