Element 1 · Reactive nonmetal
Hydrogen (H) — Element 1
Greek hydro genes — water-forming
Hydrogen (H) is a reactive nonmetal in Period 1, Group 1 of the periodic table with atomic number 1, standard atomic weight 1.008 u, and ground-state electron configuration 1s¹. At standard temperature and pressure it is classified as a gas with 1 valence electron and common oxidation states +1, -1.
Ammonia production, fuel cells, rocket fuel
What are the atomic properties and physical constants of Hydrogen?
Reference constants compiled from IUPAC standard atomic weights, the NIST Atomic Spectra Database, and the CRC Handbook.
- Atomic number (Z)
- 1
- Standard atomic mass
- 1.008 u
- Chemical family
- Reactive nonmetal
- Ground-state configuration
- 1s¹
- Electrons per shell
- 1
- Valence electrons
- 1
- Common ion charges / oxidation states
- +1, -1
- Phase at STP
- Gas
- Pauling electronegativity
- 2.20 Pauling
- First ionization energy
- 1,312 kJ/mol
- Atomic radius
- 53 pm
- Melting point
- -259 °C
- Boiling point
- -253 °C
- Discovery year
- 1766
- Table coordinate
- Period 1, Group 1
- Radioactivity
- Has stable isotope(s)
How are electrons arranged across Hydrogen’s shells?
A neutral Hydrogen atom contains 1 electron distributed across 1 occupied principal energy shell (1s¹). The table below compares Hydrogen’s shell occupancy against each shell’s theoretical 2n² capacity.
| Principal Shell (n) | Spectroscopic Letter | Electrons in H | Max Shell Capacity (2n²) |
|---|---|---|---|
| n = 1 | K | 1 e⁻ | 2 e⁻ |
Frequently Asked Questions about Hydrogen (H)
What is the atomic mass and atomic number of Hydrogen (H)?
Hydrogen (H) has atomic number Z = 1 (1 protons in its nucleus) and an IUPAC standard atomic weight of 1.008 u. It sits in Period 1, Group 1 and is classified as a reactive nonmetal.
What is the ground-state electron configuration of Hydrogen?
The neutral ground-state electron configuration of Hydrogen (Z = 1) is 1s¹. Across its 1 occupied principal shells (n = 1 to n = 1), the electrons per shell are 1, with 1 valence electron participating in bonding.
What are the common ion charges and electronegativity of Hydrogen?
Hydrogen commonly forms +1, -1 oxidation states or ion charges in compounds. Its Pauling electronegativity is 2.20 and its first ionization energy is 1,312 kJ/mol.
When was Hydrogen discovered and what is it used for?
Hydrogen was discovered in 1766 (Greek hydro genes — water-forming). Ammonia production, fuel cells, rocket fuel
How does Hydrogen compare to neighboring elements?
Other reactive nonmetal elements: