Calcium as are all of the elements are designated usually by The First and second letter in its name. In this case Calcium the first two letters are Ca with the first letter Upper Case. It is or does not have a chemical formula but in nature exists mainly as a +2 valence cation bound to one -2 charged anion or two -1 charged anions like chloride, or any of the halides. For example...Calcium pure calcium is less stable that let's say CaCl2 or Calcium Chloride. By becoming salts the element calcium gives up two electrons (giving it a +2) charge, and the chloride ateoms each have an affinity each for one electron. Now we have two ionically charged species that would like to bond inoically (very strong, very stable, more stable than in pure elemental form). So nature has its way of stabilizing an element by binding inionically in this case.