Silicon (Si)
Silicon is the 14th element, a metalloid in the p-block. Its standard atomic weight is 28.086.
Silicon
28.086
What the table records
- Atomic number
- 14
- Standard atomic weight
- 28.086
- Group
- 14
- Period
- 3
- Block
- p-block
- Category
- Metalloid
- [Ne] 3s2 3p2
- Valence electrons
- 4
- Typical valence
- 4
- Van der Waals radius
- 2.1 Å
- Covalent radius
- 1.11 Å
Molecules containing silicon
The lightest named structures in this library that contain Si.
Silicon
Si · 28.09 g/mol
Silyl
H₃Si · 31.11 g/mol
Silane
H₄Si · 32.12 g/mol
Silicon carbide
CSi · 40.1 g/mol
Silanol
H₄OSi · 48.12 g/mol
Silica
O₂Si · 60.08 g/mol
Trimethylsilane
C₃H₁₀Si · 74.2 g/mol
Disiloxane
H₆OSi₂ · 78.22 g/mol
(Trimethylsilyl)amide
C₃H₁₀NSi- · 88.21 g/mol
Monosilylacetamide
C₂H₇NOSi · 89.17 g/mol
[SIMe3O]-
C₃H₉OSi- · 89.19 g/mol
Silicate
O₄Si-4 · 92.08 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.