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 Enhanced Bohr Model Bohr Model Orbital Diagram

Properties

Atomic Radius
25 pm
Atomic Volume
Covalent Radius
32 pm
Metallic Radius
Ionic Radius
-38 pm
Crystal Radius
-24 pm
Van der Waals radius
110.00000000000001 pm
Density
0.000082 g/cm³
Boiling Point
20.28 K
Melting Point
14.01 K
Electrons per shell1
Electronegativity
2.2
Electrophilicity
2.0047699914014 eV/particle
Proton Affinity
Electron Affinity
0.754195 eV/particle
Ionization Potential
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
Molar Heat Capacity
28.836 J/(mol K)
Specific Heat Capacity
14.304 J/(g⋅K)
Thermal Conductivity
0.1815 W/(m K)
Gas Basicity
Dipole Polarizability
4.50711 a₀
C6 Dispersion Coefficient
6.499026705 a₀
Oxidation States-1, 1
Color
Colorless
Crystal StructureSimple Hexagonal (HEX)
Lattice Constant
3.75 Å
Bulk Modulus
Electrical Resistivity
Electron Configuration1s1
Magnetic Ordering
Magnetic Susceptibility
PhaseGas
Poisson Ratio
Shear Modulus
Young's Modulus
Allotropes
Alternate Names
Adiabatic Index
Appearance
Electric Conductivity
Critical Pressure
Critical Temperature
Curie Point
Electrical
Hardness
Magnetic Susceptibility
Magnetic
Neel Point
Neutron Cross Section
Neutron Mass Absorption
Gas Phase
Quantum Numbers
Refractive Index
Space Group
Speed of Sound
Superconducting Point
Thermal Expansion
Valence Electrons
Classification
CategoryOther nonmetals, Nonmetals
CAS GroupIA
IUPAC GroupIA
Glawe Number103
Mendeleev Number105
Pettifor Number103
Geochemical Classvolatile
Goldschmidt Classatmophile
Radioactivity
RadioactiveNo
Decay Mode
Half-Life
Lifetime
Abundance
Abundance in Earth's crust
1,400 mg/kg
Abundance in Oceans
108,000 mg/L
Abundance in Human Body
Abundance in Meteor
Abundance in Sun
Abundance in Universe75%

Isotopes of Hydrogen

Stable Isotopes
1H 2D
Unstable Isotopes
3T 4H 5H 6H 7H

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
Name OriginGreek: hydro (water) and genes (generate)
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.