Scources+Sited_farrahbakr_

**__SCOURCES SITED (BIBLIOGRAPHY)

http://www.chem4kids.com/files/elements/art/020_symbol.gif

http://en.wikipedia.org/wiki/Calcium

http://www.saburchill.com/chemistry/visual/atoms/images/Ca.jpg

http://www.worldofmolecules.com/elements/calcium.htm__

http://www.lenntech.com/Periodic-chart-elements/ca-en.htm#Environmental%20effects%20of%20calcium**