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1 H Hydrogen 1.008

Nonmetal

Hydrogen 氢

1s¹

  • Period 1
  • Group 1
  • Block s
  • Gas

Electron configuration

1s¹

Orbital diagram (valence)

1s ↑
Electrons per shell
1
Unpaired electrons
1
Zeff (Slater)
1.00

Properties

Atomic weight
1.008
Electronegativity (Pauling)
2.2
First ionization energy
1312 kJ/mol
Electron affinity
72.75 kJ/mol
Covalent radius
31 pm
van der Waals radius
120 pm
Melting point
13.81 K
Boiling point
20.28 K
Density
8.988 × 10⁻⁵ g/cm³
Melting / boiling point
−259.3 °C / −252.9 °C
Common oxidation states
+1, −1
Discovered
1766

Natural isotopes

12m/z020406080100Abundance / %
Mass number AAtomic mass / uAbundance
1H1.00782599.99 %
2H2.0141020.0115 %

Isotope masses: AME2020; abundances: IUPAC/CIAAW representative values.

Emission spectrum

Hydrogen discharge tube · pink-magenta

Explore in the spectroscope lab

Successive ionization energies

1: 13.60 eV1n-th electron removed10Ionization energy / eV (log)

The big jumps appear where core electrons start to be removed. Ionization energies from the NIST Atomic Spectra Database.

Hydrogen in the course

The lessons that discuss this element most (ranked by mentions).

Lab experiments with Hydrogen

Standard reduction potentials

2 HX+(aq)+2 eX−→HX2(g)\ce{2H+(aq)} + \ce{2e-} \mathrel{\ce{->}} \ce{H2(g)}0.000 V
2 HX2O(l)+2 eX−→HX2(g)+2 OHX−(aq)\ce{2H2O(l)} + \ce{2e-} \mathrel{\ce{->}} \ce{H2(g)} + \ce{2OH-(aq)}−0.828 V
All potentials

Periodic trend

H: 1312 kJ/molHe: 2372 kJ/molLi: 520.2 kJ/molBe: 899.5 kJ/molB: 800.6 kJ/molC: 1086 kJ/molN: 1402 kJ/molO: 1314 kJ/molF: 1681 kJ/molNe: 2081 kJ/molNa: 495.8 kJ/molMg: 737.7 kJ/molAl: 577.6 kJ/molSi: 786.5 kJ/molP: 1012 kJ/molS: 999.6 kJ/molCl: 1251 kJ/molAr: 1521 kJ/molK: 418.8 kJ/molCa: 589.8 kJ/molSc: 633 kJ/molTi: 658.8 kJ/molV: 650.9 kJ/molCr: 652.9 kJ/molMn: 717.3 kJ/molFe: 762.4 kJ/molCo: 760.4 kJ/molNi: 737.1 kJ/molCu: 745.4 kJ/molZn: 906.4 kJ/molGa: 578.8 kJ/molGe: 762.2 kJ/molAs: 947 kJ/molSe: 940.9 kJ/molBr: 1140 kJ/molKr: 1351 kJ/molRb: 403 kJ/molSr: 549.5 kJ/molY: 599.8 kJ/molZr: 640.1 kJ/molNb: 652.1 kJ/molMo: 684.3 kJ/molTc: 702.4 kJ/molRu: 710.2 kJ/molRh: 719.7 kJ/molPd: 804.4 kJ/molAg: 731 kJ/molCd: 867.8 kJ/molIn: 558.3 kJ/molSn: 708.6 kJ/molSb: 833.6 kJ/molTe: 869.3 kJ/molI: 1008 kJ/molXe: 1170 kJ/molCs: 375.7 kJ/molBa: 502.9 kJ/mol 0510152025303540455055Atomic number Z05001000150020002500First ionization energy / kJ/mol

Group 1

Data: PubChem periodic table (public domain); atomic weights are IUPAC abridged standard values; covalent radii from Cordero et al. (2008).