Question: why is calcium and why its important?

Nicolas Biber answered on 13 Jun 2011:

Calcium is the twentieth element. This means that its atoms have twenty protons and (in their uncharged state) twenty electrons. Protons and electrons are the charged particles in atoms. The number of protons determines what element the atom belongs to.
In nature we mostly encounter calcium in a bond with carbon, calcium carbonate, which is simply lime stone. Calcium is the fifth most abundant element in the Earth’s crust. It is important for all living things because it works as a signalling substance in cells in its charged state, the calcium 2+ ion. Calcium becomes charged when it gives off two electrons. Charged atoms, ions, are very reactive, they like to bind to other atoms. In this way they change molecules in our body for a short time, which is interpreted as a signal by the body to do something. Calcium is also important to building a skeleton. Unfortunately cell biology is not my speciality, but I hope I was able to answer your question