| Symbol | Ca |
| Atomic number | 20 |
| Group | 3 (Scandium group) |
| Period | 4 |
| Block | d |
| Classification | Alkaline Earth Metal |
| Appearance | - |
| Color | Silver |
| Number of protons | 20 p+ |
| Number of neutrons | 20 n0 |
| Number of electrons | 20 e- |
| Phase at STP | Solid |
| Density | 1.55 g/cm3 |
| Atomic weight | 40.0784 u |
| Melting point | 1115 K 841.85 °C 1547.33 °F |
| Boiling point | 1757 K 1483.85 °C 2702.93 °F |
| Heat of vaporization | 154.67 kJ/mol |
| Electronegativity (Pauling Scale) | 1 |
| Electron affinity | 2.37 kJ/mol |
| Oxidation states | +1, +2 (a strongly basic oxide) |
| Ionization energies |
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| Discovery and first isolation | Humphry Davy (1808) |
Discovery of calcium Calcium compounds were known for millennia, although their chemical makeup was not understood until the 17th century. Lime as a building material and as plaster for statues was used as far back as around 7000 BC. Vitruvius, a Roman architect, noted that the lime that resulted was lighter than the original limestone, attributing this to the boiling of the water. In 1755, Joseph Black proved that this was due to the loss of carbon dioxide, which as a gas had not been recognised by the ancient Romans. In 1789, Antoine Lavoisier suspected that lime might be an oxide of a fundamental chemical element. Calcium, along with its congeners magnesium, strontium, and barium, was first isolated by Humphry Davy in 1808. Following the work of Jöns Jakob Berzelius and Magnus Martin af Pontin on electrolysis. | |