At room temperature, calcium’s natural state of matter is that of a solid. Calcium is an alkaline earth metal that belongs to Group 2 on the periodic table. Its atomic number is 20, and its appearance is silvery white in color.
The Earth’s crust contains about 4.2 percent calcium. In nature, calcium does not exist in free form because it readily makes compounds with many other substances, such as water and oxygen.
In 1808, Humphry Davis was able to isolate calcium from a combination of lime and mercuric oxide through the process of electrolysis.
Today, calcium and its many compounds have many applications, including fertilizers, antacids, toothpaste, white paint and as an alloying agent.