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How to study the chemistry and physiological roles of calcium ions in the body 
Understand the difference between the metallic and ionic forms of calcium. 
The element calcium follows the trend in properties that is seen with magnesium, sodium and potassium elements. Namely, it is toxic to mammals in its metallic form, while it is benign in its ionic form.
Actually, calcium ions are not only benign but also essential for the metabolism of the body. Study the use of calcium by the body.