Hydrogen (H)
Hydrogen is the 1st element, a reactive nonmetal in the s-block. Its standard atomic weight is 1.008.
Hydrogen
1.008
What the table records
- Atomic number
- 1
- Standard atomic weight
- 1.008
- Group
- 1
- Period
- 1
- Block
- s-block
- Category
- Reactive nonmetal
- 1s1
- Valence electrons
- 1
- Typical valence
- 1
- Van der Waals radius
- 1.2 Å
- Covalent radius
- 0.31 Å
Molecules containing hydrogen
The lightest named structures in this library that contain H.
Hydride
H- · 1.01 g/mol
Hydrogen cation
H+ · 1.01 g/mol
Tetra-n-butyl titanate, polymer with water
H · 1.01 g/mol
Hydrogen
H₂ · 2.02 g/mol
Carbon(1-) monohydride
CH- · 13.02 g/mol
Borane
H₃B · 13.84 g/mol
Borohydride
H₄B- · 14.84 g/mol
Methyl
CH₃ · 15.04 g/mol
Azanide
H₂N- · 16.02 g/mol
Methane
CH₄ · 16.04 g/mol
Hydroxide
HO- · 17.01 g/mol
Hydroxyl
HO · 17.01 g/mol
How to read these numbers
The standard atomic weight is an average over the isotopes as they occur naturally, which is why it is rarely a whole number. It is the figure a molar mass calculation uses. Work in mass spectrometry wants the monoisotopic mass of a single isotope instead, which is a different number.
The two radii are not the same measurement. The covalent radius is half the distance between two bonded atoms of the element; the van der Waals radius is how close a non-bonded atom gets before repulsion takes over, and is always the larger. Space-filling models are drawn with the second, ball-and-stick models with the first — which is why the same molecule looks so different in the two.