Calcium: The Element in Bones, Chalk and Hard Water
Calcium is a metallic element essential to living things. Its name comes from the Latin for lime, and its compounds build bones, shells, chalk and cement.
Calcium is the chemical element with symbol Ca and atomic number 20. Pure calcium is a soft silvery metal that nobody encounters casually. What people actually meet are its compounds: the calcium carbonate of chalk, shells and limestone, and the calcium phosphate of bone and teeth.
- A chemical element (Ca). *Calcium reacts vigorously with water.*
- A dietary mineral. *Dairy products are high in calcium.*
- Deposits in water or on surfaces. *Calcium build-up in the kettle.*
Word forms
| Form | Word | Example |
|---|---|---|
| Noun | calcium | A calcium supplement. |
| Adjective | calcareous | Calcareous soil. |
| Verb | calcify | The tissue had calcified. |
| Noun | calcification | Calcification of the artery. |
| Compound | calcium carbonate | Chalk is calcium carbonate. |
How it is used in a sentence
- Children need calcium for growing bones.Uncountable, no article.
- Hard water leaves calcium deposits in pipes.Really calcium and magnesium salts.
- The debate has calcified into two fixed positions.Figurative — hardened and unable to change.
Where you meet its compounds
- Limestone and chalk — calcium carbonate laid down by ancient marine life
- Bone and teeth — mainly calcium phosphate
- Shells and coral — calcium carbonate again
- Plaster and cement — made by heating limestone to drive off carbon dioxide
- Quicklime — calcium oxide, the *calx* that gave the element its name
Named by Humphry Davy in 1808 from Latin *calx*, lime, when he first isolated the metal by electrolysis. The same *calx* gives calculate: Roman counting used small limestone pebbles called *calculi*.
Is calcium a metal?
Yes, an alkaline earth metal. It is only unfamiliar as a metal because it tarnishes and reacts too readily to sit around in pure form.
What does calcified mean figuratively?
Set hard and no longer able to change — used of attitudes, institutions and arguments.