Wikijunior:The Elements/Calcium

What does it look and feel like?
Calcium is a soft, gray metal. When it burns, it burns with a yellowish-red flame. When it is exposed to air, it develops a gray-white coating because it reacts with the oxygen in the air to form a coating of calcium oxide (lime.)

Strongly alkaline and reactive with any body fluids such as sweat, calcium metal burns flesh exposed to it. Do not touch it.

How was it discovered?
Calcium has been known since Ancient Roman times. The Romans discovered a way to make calcium oxide by heating limestone in a furnace. However, it wasn't until 1808 that pure calcium was isolated by Sir Humphrey Davy.

Where did its name come from?
Calcium gets its name from calcis, which is a Latin word that means lime.



Did You Know?
 * As wet calcium hydroxide combines with air it becomes hard calcium carbonate. This chemical reaction is what causes cement to harden.
 * Calcium is the most common metal in animals.
 * Stalactites and stalagmites are made primarily of calcium carbonate.

Where is it found?
Calcium is not found pure as an element due to its great tendency to react with other elements to form compounds, but it is commonly found in the compound calcium carbonate (CaCO3). Many rocks such as limestone, marble, chalk, and calcite contain this substance. Limestone caves are a great example of where calcium can be found. Seashells and snail shells are primarily of calcium carbonate. Eggshells are mostly made from this compound too.

Calcium is also found in significant amounts in many foods. Dairy products like milk, yogurt and cheese contain calcium. Green vegetables also often have calcium. Broccoli, collard greens, almonds, sesame seeds, and beans all contain significant amounts of calcium.



What are its uses?
Calcium is important for our body to run. It helps build strong bones and teeth, and it allows our muscles and brain cells work.

Calcium is an important substance in the building industry, because calcium hydroxide (Ca(OH)2 is used in cement and mortar. Calcium carbonate is also used in plastics and adhesives as a filler. Because calcium oxide (CaO) neutralizes acid it can be used to decrease the effects of acid rain in rivers and lakes. Calcium is also commonly used in heartburn and antacid tablets.

Is it dangerous?
Calcium metal burns hot if ignited, and it reacts violently with water to form the strongly-alkaline calcium hydroxide that can cause chemical burns.

Calcium compounds aren't dangerous unless they are strongly alkaline or acidic or if they are poisonous due to the other parts of the compound. Calcium compounds are nearly everywhere in our bodies. In fact, calcium is an essential nutrient that is needed by the human body to help build strong bones and teeth.

Calcium metal has a very high boiling/melting point.