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Calcium is the fifth most plentiful element in the Earth's crust.
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It is also the fifth most abundant element found dissolved in the oceans.
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Calcium has been in use for over 16,000 years, but was formally isolated in 1808 by Sir Humphry Davy.
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It is not found in its natural state, but is found commonly in minerals and in its compounds.
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There are fifteen recognized compounds for calcium, all with unique industrial uses.
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Calcium is used in the creation of hydrogen, as it reacts with water to give off the gas.
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Calcium is slow to react in water because it is coated in an insoluble calicum hydroxide.
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Calcium is the lightest of the alkaline earth metals with a density of 1.55 g/cm3.
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There are two allotropes of of calcium.
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Calcium is the fifth more prevalent element in the human body.
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It has many functions in the body, but mostly it is used to provide support for the skeleton.
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There is approximately one kilogram of calcium in an average-sized human skeleton.
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Calcium's high atomic number is what allows human bones to show up under Xray.
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Calcium joins with phosphate to form hydroyxlapatite, the main component in bones and tooth enamel.
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Calcium has four stable isotopes and two unstable isotopes.
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The half-lives of the unstable calcium isotopes are so long that they may be considered almost stable.
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Ca-41 decays to an isotope of potassium, and scientists use this decay as an indication of anomalies in solar systems.
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Calcium and most of its compounds are fairly low in toxicity.
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Calcium has very few environmental dangers.
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When consumed in excess, however, calcium overdose can lead to kidney failure.
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