Silicon
Silicon is a chemical element with the symbol Si and atomic number 14. It has a standard atomic weight of 28.085, sits in period 3 and group 14, and is classified as a metalloid.
Properties
| Symbol | Si |
|---|---|
| Atomic number | 14 |
| Standard atomic weight | 28.085 |
| Category | Metalloid |
| Group | 14 |
| Period | 3 |
| Electron configuration | [Ne] 3s2 3p2 |
| Outer-shell electrons | 4 |
The figure of 28.085 is a conventional value, because IUPAC publishes an interval for this element rather than a single weight. For elements like this one the fourth digit carries real uncertainty, because the isotopic composition varies measurably between natural sources — so quoting eight digits would overstate what is known.
Compounds containing silicon
5 of the compounds in this reference contain Si, listed by the fraction of their mass it makes up.
| Compound | Formula | Atoms | % by mass |
|---|---|---|---|
| silicon carbide | CSi | 1 | 70.0% |
| quartz | O2Si | 1 | 46.7% |
| silicon dioxide | O2Si | 1 | 46.7% |
| sodium metasilicate | Na2O3Si | 1 | 23.0% |
| sodium silicate | Na2O3Si | 1 | 23.0% |
Calculate with silicon
- Molar mass of any formula containing it
- Electron configuration, including ions
- Effective nuclear charge by Slater's rules
- Average atomic mass from isotope abundances
Group 14
Atomic weights are the IUPAC 2021 standard values, abridged to the conventional five significant figures. Group, period, category and electron configuration are derived from the atomic number rather than stored, so they cannot drift out of step with it.