Calcium (20)

Calcium as the element is a grey silvery metal. The metal is rather hard. Calcium is an essential constituent of leaves, bones, teeth, and shells. Calcium is the fifth most abundant element in the earth's crust and makes up more than 3% of the crust. Calcium does not occur as the metal itself in nature and instead is found in various minerals including as limestone, gypsum and fluorite. Stalagmite...s and stalactites contain calcium carbonate (CaCO3). Calcium carbonate is the basis of the cement industry.

Calcium is classified chemically as one of the alkaline earth elements (that is, in Group 2 of the periodic table. The metal is rather reactive. It readily forms a white coating of calcium nitride (Ca3N2) in air. It reacts with water and the metal burns with a yellow-red flame, forming largely the nitride.

•Name: Calcium
•Symbol: Ca
•Atomic number: 20
•Atomic weight: 40.078
•Standard state: solid at 298 K
•CAS Registry ID: 7440-70-2
•Group in periodic table: 2
•Group name: Alkaline earth metal
•Period in periodic table: 4
•Block in periodic table: s-block
•Color: silvery white
•Classification: Metallic

Historical information

Calcium was discovered by Sir Humphrey Davy at 1808 in England. Origin of name: from the Latin word "calx" meaning "lime". Compounds such as lime (CaO, calcium oxide) were prepared by the Romans in the first century under the name calx (used in explosive devices). Literature dating back to about 975 AD notes that plaster of paris (calcium sulphate, CaSO4, dehydrated gypsum) is useful for setting broken bones. Other calcium compounds used in early times include limestone (CaCO3, calcium carbonate).

Calcium metal was not isolated until 1808. After learning that Berzelius and Pontin prepared calcium amalgam by electrolysing lime in mercury, Sir Humphry Davy was able to isolate the impure metal. He did this by the electrolysis of a mixture of lime and mercuric oxide (HgO). Calcium metal was not available in large scale until the beginning of the 20th century.

Sometime prior to the autumn of 1803, the Englishman John Dalton was able to explain the results of some of his studies by assuming that matter is composed of atoms and that all samples of any given compound consist of the same combination of these atoms. Dalton also noted that in series of compounds, the ratios of the masses of the second element that combine with a given weight of the first element can be reduced to small whole numbers (the law of multiple proportions). This was further evidence for atoms. Dalton's theory of atoms was published by Thomas Thomson in the 3rd edition of his System of Chemistry in 1807 and in a paper about strontium oxalates published in the Philosophical Transactions. Dalton published these ideas himself in the following year in the New System of Chemical Philosophy.

Physical properties

•Melting point: 1115 [or 842 °C (1548 °F)] K
•Boiling point: 1757 [or 1484 °C (2703 °F)] K
•Density of solid: 1550 kg m-3

Orbital properties

•Ground state electron configuration: [Ar].4s2
•Shell structure: 2.8.8.2
•Term symbol: 1S0

Isolation

Calcium metal is readily available commercially and there is no need to make it in the laboratory. Commercially it can be made by the electrolysis of molten calcium chloride, CaCl2.

Cathode: Ca2+(l) + 2e- → Ca                                                       Anode: Cl-(l) → 1/2Cl2 (g) + e-

The calcium chloride is made by the action of hydrochloric acid upon calcium carbonate. Calcium chloride is also a byproduct in the Solway process used to make sodium carbonate:

CaCO3 + 2HCl → CaCl2 + H2O + CO2

Alternatively, and on small scale, calcium can be made through the reduction of CaO with aluminium or of CaCl2 with sodium metal:

6CaO + 2Al→ 3Ca + Ca3Al2O6

CaCl2 + 2Na→ Ca + 2NaCl

Interesting Facts:

1. It’s a metal, shiny and silvery like other metals. It is not white powder as most people think. It is a silvery white, soft alkaline earth metal.

2. Then why tablets are white? The white coating on calcium metal is an element that has reacted with the oxygen in the air and formed calcium oxide

3. It is obtained from chalk, limestone, and marble

4. There are 179 different known uses for Ca in the human body.

5. More than 99% of total body calcium is stored in the bones and teeth

6. Bones are actually a composition of protein strengthened by deposits of Ca.

7. This important elements is essential for strong bones

8. When the body is injured, it starts the healing process by stopping a blood with a blood clot.

4. It is one of the more difficult elements for the body to digest.

5. Vitamin D is needed to absorb it.

6. It can be obtained from a variety of foods. Milk and dairy products are the biggest sources.

7. It is basic component of most plants and animals as well.

8. It is very important and sometimes even essential for people with osteoporosis, colon cancer and high blood pressure.

9. Calcium is the fifth most abundant element in the earth’s crust and makes up more than 3% of the crust.

10. Human breast milk provides all the calcium a child needs.

11. People need extremely regulated calcium level because our brains rely on it. If the level is too high or too low, our nervous system gets “nervous”

12. Dark green leafy vegetables are a much better source of calcium than milk. They have almost no fat calories

13. Caffeine is “washing away” calcium. So don’t forget to add milk or cream to your morning coffee!

14. In nature, Ca carbonate is often found in nature in caves in stalagmites

15. The element name “calcium” comes from the Latin word “calcis” meaning “lime”

16. Interesting chemistry facts about an element

17. How much calcium does a human body need?
               

AGE	AMOUNT OF CALCIUM (mg)
Birth – 6 months	210
6 to 12 months	270
1 to 3 years	500
4 to 8 years	800
9 to 18 years	1300
19 to 50 years	1000
50 and older	1200