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1 H 1.00794(7)

Hydrogen

Nonmetal
Symbol H
Atomic Number 1
Atomic Weight 1.00794(7)
CAS Registry ID 1333-74-0
Group Name (none)
Period Number 1
Block s-block
State at STP Solid

Description

Sample of Hydrogen ⌕ Enlarge Image

Hydrogen, with an atomic weight of 1.0079, is the lightest element known. It is estimated that 90% of the weight of the universe is composed of hydrogen. In its normal physical state, hydrogen is a colorless and odorless gas. Hydrogen has a melting point of - 434.45 °F and a boiling point of - 427.17 °F. The most common uses of hydrogen include: hydrogenation of fats and oils, as a nitrogen fixative, as a liquid for cryogenic purposes, and to reduce metallic ores.

Isolation

Here is a brief summary of the isolation of hydrogen.

Hydrogen ⌕ Enlarge Image

The isolation procedures of hydrogen depend on how much hydrogen needs to be isolated, and what equipment is available for the isolation procedures. For small isolation procedures of hydrogen gas in a laboratory, one part of calcium hydride is reacted with two parts of water; the end product is a small amount of hydrogen gas. Another isolation method that can be conducted in a laboratory uses the reaction between iron filings and dilute sulphuric acid; as with the previous formula the result is a small quantity of hydrogen gas.

Large amounts of hydrogen gas can be isolated for industrial uses through two main methods. The first method is a process in which coke is heated with steam to promote the water gas shift reactions. In the second reaction hydrocarbons, like methane, are heated with steam; the end products from both of these isolation methods are hydrogen gas and carbon monoxide. Additional hydrogen gas can be produced by passing the carbon monoxide and steam over iron oxide or cobalt oxide at a temperature of 732 °F.

General

NameHydrogen
SymbolH
Number1
Chemical seriesNonmetal
Group1
Period1
Blocks
Appearancecolorless
Standard atomic weight1.00794(7) g·mol⁻¹
Electron configuration1s1
Electrons per shell1

Atomic Properties

Crystal structurehexagonal
Oxidation states1, −1
Electronegativity2.1 (Pauling scale)
Ionization energies
Atomic radius25 pm
Atomic radius (calc.)53 pm
Covalent radius37 pm
Van der Waals radius

Physical Properties

Phasegas
Density (near r.t.)(0 °C, 101.325 kPa)
Liquid density at m.p.
Melting point14.01 K (−259.14 °C, −434.45 °F)
Boiling point20.28 K (−252.87 °C, −423.17 °F)
Critical point
Heat of fusion(H2) 0.117 kJ·mol−1
Heat of vaporization(H2) 0.904 kJ·mol−1
Heat capacity(25 °C) (H2) 28.836 J·mol−1·K−1

Miscellaneous

Magnetic ordering
Electrical resistivity
Thermal conductivity(300 K) 180.5 m W·m−1·K−1
Thermal expansion
Speed of sound (thin rod)(gas, 27 °C) 1310 m/s
Young's modulus
Shear modulus
Bulk modulus
Poisson ratio
Mohs hardness
Vickers hardness
Brinell hardness