Chemical element · Atomic number 1
Hydrogen
Hydrogen in the periodic table: atomic number 1, electron configuration, atomic mass, physical data, oxidation states, media credit and visible sources.
Nonmetal
gaseous
1.0080 u
Documented element sampleLabelled ampoules for hydrogen, deuterium and tritium; the samples are not visible through the glass.
Image credit: James St. John
Auto-oriented, limited to 1600 × 1200 pixels and re-encoded as WebP; the subject was not altered.
Atomic classification
Shell occupancy
Hydrogen in the Bohr shell model
This shows the electron distribution of the neutral atom in a simplified shell model.
- K · n=1
- 1 electron
- Electron configuration
- 1s1
- Electrons per shell
- 1
- Group
- 1
- Period
- 1
- Block
- S
- Element category
- Nonmetal
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Physical and chemical properties
- Atomic mass
- 1.0080 u
- Standard state
- gaseous
- Density
- 0.00008988 g/cm³
- Melting point
- 13.81 K
- Boiling point
- 20.28 K
- Electronegativity
- 2.2 (Pauling)
- First ionisation energy
- 13.598 eV
- Oxidation states
- +1, -1
- Discovery
- 1766
Safety and periodic classification
Safety
Safe handling cannot be inferred from Hydrogen's position in the periodic table alone. Laboratory, classroom and disposal decisions must follow the documentation for the exact material and its safety data sheet.
Position and comparison
Hydrogen is in period 1, group 1 and the S block. Its direct successor by atomic number is Helium. The recorded Pauling electronegativity is 2.2. Periodic trends are compared only through the separately sourced neighbouring values.
Sources and scope
PubChem attributes element data to sources including IUPAC, NIST and IAEA. Quanta stores the referenced snapshot locally and leaves unknown values unavailable.