Calcium has 20 protons, 20 neutrons and 20 electrons. It is a silvery solid that is classified as an Alkaline Earth metal on the periodic table.
The element calcium is never found alone in nature; it is always in compound form with other elements because it reacts easily with oxygen and water. In 1808, Sir Humphry Davy was able to isolate calcium atoms. There is little use for metallic calcium. Rather, most use comes from one of its many compounds. Calcium carbonate is used to make chalk, toothpaste, white paint and antacids. The calcium found in teeth and bones is the compound calcium phosphate.