Calcium (Ca)
Alkaline earth metal · s-block · period 4 · group 2
Soft, silvery-grey reactive metal.
Calcium (symbol Ca) is chemical element number 20, a alkaline earth metal in group 2, period 4 of the periodic table. Its standard atomic weight is 40.078 and its electron configuration is [Ar] 4s2. At room temperature it is a solid. The fifth most abundant element in the Earth's crust.
Properties
| Atomic number | 20 |
|---|---|
| Atomic mass | 40.078 |
| Category | Alkaline earth metal |
| Block | s-block |
| Group · Period | 2 · 4 |
| Electron configuration | [Ar] 4s2 |
| Electrons per shell | 2, 8, 8, 2 |
| State at 25 °C | solid |
| Melting point | 1115 K |
| Boiling point | 1757 K |
| Density | 1.55 g/cm³ |
| Electronegativity (Pauling) | 1 |
| Radioactive | No |
| Origin | primordial |
| Discovered | 1808 · Humphry Davy |
Key facts about Calcium
- The fifth most abundant element in the Earth's crust.
- Locked up as calcium phosphate, it makes your bones and teeth rigid.
- Limestone, chalk, marble and seashells are all calcium carbonate.
- Quicklime (CaO) plus water releases enough heat to boil the water.
What Calcium is used for
Cement and mortar, steelmaking, dietary supplements, plaster, water treatment.
Where it sits in the periodic table
Calcium is in group 2, period 4, of the s-block. Its electron configuration [Ar] 4s2 means its outermost shell holds 2 electrons, which is what places it here and explains much of its chemistry. See Calcium on the interactive table →
Calcium — frequently asked questions
What is Calcium used for?
Cement and mortar, steelmaking, dietary supplements, plaster, water treatment.
Is Calcium radioactive?
No. Calcium has at least one stable isotope and is not radioactive.
What is the electron configuration of Calcium?
Calcium has the electron configuration [Ar] 4s2, which is 2, 8, 8, 2 electrons per shell.
What group and period is Calcium in?
Calcium is in group 2, period 4, in the s-block. Its outer shell holds 2 electrons.
Who discovered Calcium?
Calcium was discovered in 1808 by Humphry Davy.