Everyone needs calcium. The main place to find calcium is in milk. When we are children, our parents always make us drink milk because it contains calcium. Calcium helps make our bones grow strong. Even though adults need strong bones, children’s bones are growing.
They are actually weaker and softer than adult bones. However, some adults and children are lactose intolerant. So, they must get their calcium from other foods and drinks. Over average it is about 1,100 milligrams of milk per day. It varies slightly for women who are older than 50 years old and those who are younger than 50 years old. However, it is recommended that you do not get too much calcium or it could hurt your body.
Calcium does not do well outside of a dry atmosphere. Calcium carbonate forms a salty-looking crust on the surface of the earth when it has been exposed to the air for a day or more. Calcium is a silvery white metal. Its surface is covered with a thin layer of oxide that helps protect the metal from the air.
Calcium mixed with water forms an alkaline substance important in maintaining the health of e.g. the coral reefs. Limewater solution is less prone to degradation by atmospheric carbon dioxide than when it is found in a still water reservoir.
If pure calcium metal is kept out in the air, it is slowly oxidized and calcium oxide is formed. Also, calcium nitride may be formed in small amount in dry air but the oxide will predominate because of the greater reactivity with oxygen overcompensate for the higher concentration of nitrogen.
If moisture is present, the calcium oxide form may further react with water to form the hydroxide (calcium hydroxide) or react with carbon dioxide to form calcium carbonate.
The calcium oxide, hydroxide and carbonate all form a white coating on the surface of the metal piece.