hydrogen

• Description
• General information
• Physical data
• Radii
• Electronegativities
• Solid state structure
• Temperatures
• Enthalpies
• Ionization Enthalpies
• Isotopes
• Further information

Description

Hydrogen is the lightest element and is by far the most abundant element in the universe, making up about about 90% of the universe by weight. Hydrogen as water (H₂O) is absolutely essential to life and is present in all organic compounds. Hydrogen gas was used in lighter-than-air balloons for transport but is far too dangerous because of the fire risk (Hindenberg).

General information

Discoveror: Henry Cavendish
Date discovered: 1766
Discovered at: London, England
Meaning of name: From the Greek words "hydro" and "genes" meaning "water" and "generator"

Physical data

Standard state: gas (the lightest known gas)
Colour: colourless
Density of solid at ambient temperature/kg m^-3: no data
Molar volume/cm³: 11.42

Radii /pm

Atomic: 60
Covalent (single bond):
Pauling radius for the ion [H]^-: 208

Valence shell orbital radius maxima (R_max)

orbital	s	p	d	f
radius	52.9	no data	no data	no data

Electronegativities

Both values are quoted on the Pauling scale.

Pauling: 2.20
Allred Rochow: 2.20

Crystal Structure

structure: hcp (hexagonal close-packed)

The following CrystalMaker image represents the solid state structure. For most elements, the most stable allotrope is illustrated. Try WebElements version 2 for interactive virtual reality and CHIME images.

Temperatures (/K)

melting point: 14.01
boiling point: 20.28

Enthalpies /kJ mol^-1

fusion: 0.117
vaporization: 0.91

single bond enthalpies:

H-F	H-Cl	H-Br	H-I	H-H
565	428	362	295	435.990

Ionization enthalpies /kJ mol^-1

Number	Enthalpy
1st	1312.0

Isotopes

This section gives some data for naturally occurring isotopes.

Nominal mass	Accurate mass	% natural abundance
1H	1.007825035 (12)	99.985 (1)
2H	2.014101779 (24)	0.015 (1)

Further Information

• Additional information about WebElements 1.2.2
• This is a licensed copy (here is the full list) of WebElements 1.2.2 and contains a subset of the material contained within the main version of WebElements (version 2)
• For further information please try WebElements version 2
• Sheffield Chemdex: perhaps the largest internet chemistry directory
• Sheffield Chemputer: interactive chemistry calculators on the WWW