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Substance Name: Hydrogen
RN: 1333-74-0


  • The first chemical element in the periodic table with atomic symbol H, and atomic number 1. Protium (atomic weight 1) is by far the most common hydrogen isotope. Hydrogen also exists as the stable isotope DEUTERIUM (atomic weight 2) and the radioactive isotope TRITIUM (atomic weight 3). Hydrogen forms into a diatomic molecule at room temperature and appears as a highly flammable colorless and odorless gas.

Molecular Formula

  • H2

Molecular Weight

  • 2.0159

Classification Code

  • Simple Asphyxiant
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Links to Resources

Names and Synonyms

Name of Substance

  • Hydrogen

MeSH Heading

  • Hydrogen


  • EINECS 215-605-7
  • H
  • HSDB 5026
  • Hydrogen
  • Hydrogen atoms
  • Molecular hydrogen
  • Protium

Systematic Name

  • Hydrogen

Superlist Names

  • Hydrogen
  • Hydrogen, compressed
  • Hydrogen, compressed [UN1049] [Flammable gas]
  • Hydrogen, refrigerated liquid (cryogenic liquid)
  • Hydrogen, refrigerated liquid (cryogenic liquid) [UN1966] [Flammable gas]
  • UN1049
  • UN1966

Registry Numbers

CAS Registry Number

  • 1333-74-0


  • 7YNJ3PO35Z

Other Registry Number

  • 725200-57-7

System Generated Number

  • 0001333740

Structure Descriptors