Ca
Calcium
Calcium is a chemical element with the symbol Ca and atomic number 20. It has a standard atomic weight of 40.078, sits in period 4 and group 2, and is classified as an alkaline earth metal.
Properties
| Symbol | Ca |
|---|---|
| Atomic number | 20 |
| Standard atomic weight | 40.078 |
| Category | Alkaline earth metal |
| Group | 2 |
| Period | 4 |
| Electron configuration | [Ar] 4s2 |
| Outer-shell electrons | 2 |
The figure of 40.078 is a standard atomic weight.
Compounds containing calcium
9 of the compounds in this reference contain Ca, listed by the fraction of their mass it makes up.
| Compound | Formula | Atoms | % by mass |
|---|---|---|---|
| calcium oxide | CaO | 1 | 71.5% |
| calcium hydroxide | CaH2O2 | 1 | 54.1% |
| fluorite | CaF2 | 1 | 51.3% |
| calcite | CCaO3 | 1 | 40.0% |
| calcium carbonate | CCaO3 | 1 | 40.0% |
| calcium phosphate | Ca3O8P2 | 3 | 38.8% |
| calcium chloride | CaCl2 | 1 | 36.1% |
| calcium sulfate | CaO4S | 1 | 29.4% |
| calcium hypochlorite | CaCl2O2 | 1 | 28.0% |
Calculate with calcium
- 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 2
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.