Hydrogen

Hydrogen (H)

Colourless, odourless gaseous chemical element. Lightest and most abundant element in the universe. Present in water and in all organic compounds. Chemically reacts with most elements. Discovered by Henry Cavendish in 1776.
Atomic Number1
Atomic Weight1.008
Mass Number1
Group1
Period1
Blocks
Protons1 p+
Neutrons0 n0
Electrons1 e-
Hydrogen discharge tube.jpg Animated Bohr Model of H (Hydrogen) Enhanced Bohr Model of H (Hydrogen) Bohr Model: H (Hydrogen) Orbital Diagram of H (Hydrogen)

Properties

Atomic Radius
25 pm
Molar Volume
Covalent Radius
32 pm
Metallic Radius
Ionic Radius
-38 pm
Crystal Radius
-24 pm
Van der Waals Radius
110 pm
Density
0.000082 g/cm³
Energy
Proton Affinity
Electron Affinity
0.754195 eV/particle
Ionization Energy
13.598434005136 eV/particle
Heat of Vaporization
0.904 kJ/mol
Heat of Fusion
0.117 kJ/mol
Heat of Formation
217.998 kJ/mol
Electrons
Electron Shells1
Valence Electrons1
Electron Configuration1s1
Oxidation States-1, 1
Electronegativity
2.2
Electrophilicity
2.00476999140139 eV/particle
Phases
PhaseGas
Gas PhaseDiatomic
Boiling Point
20.271 K
Melting Point
13.99 K
Critical Pressure
1.2858 MPa
Critical Temperature
32.938 K
Triple Point
13.8033 K
7.041 kPa
Visual
Color
Colorless
Appearancecolorless gas
Refractive Index
1.000132
Thermodynamic Properties
Thermal Conductivity
0.1815 W/(m K)
Thermal Expansion
Molar Heat Capacity
28.836 J/(mol K)
Specific Heat Capacity
14.304 J/(g⋅K)
Heat Capacity Ratio (Adiabatic Index)7/5
Electrical Properties
Type
Electrical Conductivity
Electrical Resistivity
Superconducting Point
Magnetism
Typediamagnetic
Magnetic Susceptibility (Mass)
-0.0000000248 m³/Kg
Magnetic Susceptibility (Molar)
-0.00000000004999 m³/mol
Magnetic Susceptibility (Volume)
-0.00000000223
Magnetic Ordering
Curie Point
Neel Point
Structure
Crystal StructureSimple Hexagonal (HEX)
Lattice Constant
3.75 Å
Lattice Anglesπ/2, π/2, 2 π/3
Mechanical Properties
Hardness
Bulk Modulus
Shear Modulus
Young Modulus
Poisson Ratio
Speed of Sound
1,270 m/s
Classification
CategoryOther nonmetals, Nonmetals
CAS GroupIA
IUPAC GroupIA
Glawe Number103
Mendeleev Number105
Pettifor Number103
Geochemical Classvolatile
Goldschmidt Classatmophile
Other
Gas Basicity
Dipole Polarizability
4.50711 ± 0.00003 a₀
C6 Dispersion Coefficient
6.499026705 a₀
AllotropesDihydrogen
Neutron Cross Section
0.332
Neutron Mass Absorption
0.011
Quantum Numbers2S1/2
Space Group194 (P63/mmc)

Isotopes of Hydrogen

Stable Isotopes2
Unstable Isotopes5
Radioactive Isotopes5

1H

Abundance
99.9855 ± 0.0078
Relative Atomic Mass
1.007825031898 ± 0.000000000014 Da
Mass Number1
G-Factor
5.585694702 ± 0.000000018
Half Life
Spin1/2
Quadrupole Moment
0
Discovery Year1920
Parity+

2D

Abundance
0.0145 ± 0.0078
Relative Atomic Mass
2.014101777844 ± 0.000000000015 Da
Mass Number2
G-Factor
0.857438231 ± 0.000000005
Half Life
Spin1
Quadrupole Moment
Discovery Year1932
Parity+

3T

AbundanceRadioactive ☢️
Relative Atomic Mass
3.01604928132 ± 0.00000000008 Da
Mass Number3
G-Factor
5.95792492 ± 0.000000028
Half Life
12.32 ± 0.02 y
Spin1/2
Quadrupole Moment
0
Discovery Year1934
Parity+

3T Decay Modes
Decay ModeIntensity
β (β decay)100%

4H

AbundanceRadioactive ☢️
Relative Atomic Mass
4.026431867 ± 0.000107354 Da
Mass Number4
G-Factor
Half Life
139 ± 10 ys
Spin2
Quadrupole Moment
Discovery Year1981
Parity-

4H Decay Modes
Decay ModeIntensity
n (neutron emission)100%

5H

AbundanceRadioactive ☢️
Relative Atomic Mass
5.035311492 ± 0.00009602 Da
Mass Number5
G-Factor
Half Life
86 ± 6 ys
Spin1/2
Quadrupole Moment
0
Discovery Year1987
Parity+

5H Decay Modes
Decay ModeIntensity
2n (2-neutron emission)100%

6H

AbundanceRadioactive ☢️
Relative Atomic Mass
6.044955437 ± 0.000272816 Da
Mass Number6
G-Factor
Half Life
294 ± 67 ys
Spin2
Quadrupole Moment
Discovery Year1984
Parity-

6H Decay Modes
Decay ModeIntensity
n (neutron emission)%
3n (3-neutron emission)%

7H

AbundanceRadioactive ☢️
Relative Atomic Mass
7.052749 ± 0.001078 Da
Mass Number7
G-Factor
Half Life
652 ± 558 ys
Spin1/2
Quadrupole Moment
0
Discovery Year2003
Parity+

7H Decay Modes
Decay ModeIntensity
2n (2-neutron emission)%

History

Henry Cavendish was the first to distinguish hydrogen from other gases in 1766 when he prepared it by reacting hydrochloric acid with zinc. In 1670, English scientist Robert Boyle had observed its production by reacting strong acids with metals. French scientist Antoine Lavoisier later named the element hydrogen in 1783. From the Greek word hydro (water), and genes (forming)

DiscoverersHenry Cavendish
Discovery LocationEngland
Discovery Year1766
Etymology (Name Origin)Greek: hydro (water) and genes (generate)
PronunciationHI-dreh-jen (English)
Hydrogen poses a number of hazards to safety, from fires when mixed with air to being an asphyxiant in its pure form
Hydrogen is the primary component of Jupiter and the other gas giant planets

Uses

Liquid hydrogen is used as a rocket fuel. Hydrogen is commonly used in power stations as a coolant in generators. Hydrogen's two heavier isotopes (deuterium and tritium) are used in nuclear fusion. Used as a shielding gas in welding methods such as atomic hydrogen welding. Most hydrogen is used in the production of ammonia. Also used in balloons and in metal refining. Also used as fuel in rockets. Its two heavier isotopes are: deuterium (D) and tritium (T) used respectively for nuclear fission and fusion.

Sources

Commercial quantities are produced by reacting superheated steam with methane or carbon. In lab work from reaction of metals with acid solutions or electrolysis.

Abundance
Abundance in Earth's crust
1,400 mg/kg
Abundance in Oceans
108,000 mg/L
Abundance in Human Body
10 %
Abundance in Meteor
2.4 %
Abundance in Sun
75 %
Abundance in Universe
75 %

Nuclear Screening Constants

1s0