Calcium is the most abundant metal in the human body. It is also the fifth most common element on Earth. It occurs in many minerals, such as calcite and aragonite, which are formed from calcium carbonate. Bones in animal skeletons contain calcium phosphate. Also, the hard outer layers of many other animals, such as the shells of sea snails, are made of calcium carbonate.
This element is very important in our diet, we obtain it mainly in dairy products. Antacid tablets, used to treat indigestion, contain calcium carbonate. This compound reacts with acid in the stomach. Calcium compounds are also common in building materials. Plasterboard, which is used to smooth walls, writing chalk, and gypsum are made from the mineral gypsum. Calcium oxide is an important ingredient in cement and aids in the setting process.
Summary of properties (Ca)
| Atomic weight | 40.078(4) |
| Discoverer (year) | Davy, Humphry (1808) |
| Natural form | metallic solid (face centered cubic) |
| Electron configuration | [Ar] 4s2 |
| Melting point (ºC) | 839 |
| Boiling point (ºC) | 1484 |
| Abundance in earth's crust (ppm) | 41500 |
| Isotope (abundance) | 40Ca (96.941), 42Ca (0.647), 43Ca (0.135), 44Ca (2.086), 46Ca (0.004), 48Ca (0.187) |
| Density g/cm3 | 1.55 |
| Van der Waals radius (pm) | 231 |
| Covalent radius (pm) | 174 |
| Electronegativity (Pauling) | 1.36 |
| Vaporization enthalpy (kJ/mol) | 150.00 |
| Enthalpy of fusion (kJ/mol) | 8.54 |
| Specific heat capacity (J/g·K) at 25ºC and 1 atm | 0.65 |
| Thermal conductivity (W/cm·K) at 25ºC and 1 atm | 2.010 |
| Oxidation state | +2 |
| Electron affinity (eV) | 0.02 |
| 1st Ionization potential (eV) | 6.1132 |
