Calcium (symbol Ca, atomic number 20) is the metal whose compounds build bones, teeth, shells, and limestone. It is classified as a alkaline earth metal and sits in group 2, period 4 of the periodic table.
Overview
Calcium is the chemical element with atomic number 20 and the symbol Ca. With a standard atomic weight of 40.078, it is a alkaline earth metal. In the periodic table it occupies group 2 and period 4, and under standard conditions it is normally a solid. Calcium is the metal whose compounds build bones, teeth, shells, and limestone.
Atomic structure
An atom of Calcium has 20 protons in its nucleus and, when neutral, 20 electrons arranged in the configuration [Ar] 4s2. Its standard atomic weight of 40.078 reflects the natural mix of its stable isotopes.
Discovery and place in the table
Calcium was discovered in 1808 by Humphry Davy. It follows Potassium (K) and precedes Scandium (Sc) in order of atomic number.
| Atomic number | 20 |
|---|---|
| Symbol | Ca |
| Atomic mass | 40.078 |
| Category | Alkaline earth metal |
| Group | 2 |
| Period | 4 |
| Electron configuration | [Ar] 4s2 |
| Phase at STP | Solid |
| Discovered | 1808 (Humphry Davy) |