Calcium
Calcium is essential for living organisms, in particular in cell physiology, where movement of the calcium ion Ca2+ into and out of the cytoplasm functions as a signal for many cellular processes. As a major material used in mineralization of bone, teeth and shells, calcium is the most abundant metal by mass in many animals.
Occurrence
Calcium is not naturally found in its elemental state. Calcium occurs most commonly in sedimentary rocks in the minerals calcite, dolomite and gypsum. It also occurs in igneous and metamorphic rocks chiefly in the silicate minerals: plagioclases, amphiboles, pyroxenes and garnets.
| Symbol | Ca | |
| Atomic Number | 20 | |
| Atomic Weight | 40.078 | |
| Oxidation States | +2 | |
| Electronegativity, Pauling | 1 | |
| State at RT | Solid, Metal | |
| Melting Point, K | 1112 | |
| Boiling Point, K | 1757 |
Interesting Facts about Calcium
- Calcium is the most abundant of the metallic elements in the human body. The average adult body contains about 1 kg or 2 lb of calcium, 99% of which is in the bones and teeth. Only oxygen, carbon, hydrogen and nitrogen are more abundant in our bodies than calcium.
- Calcium not only builds the structures that support our bodies, many of us also live in homes built using structural concrete or cement made with lime (calcium oxide). Snails and many shellfish use another calcium compound – calcium carbonate – to build their own homes too – their shells.
- Modern humans were not the first people to make use of calcium to build things. Egypt’s pyramids were built using limestone blocks. Limestone is crystalline calcium carbonate. In the later pyramids, the blocks were held together with gypsum or lime based mortar. Gypsum is calcium sulfate dihydrate and lime is calcium oxide.
- Have you ever wanted to be ‘in the limelight?’ Lime is calcium oxide, which produces a brilliant, intense light when burnt in an oxyhydrogen flame. It was used to light the stage in theaters during the 1800s until electricity took over – hence the saying.
- Cells in animals and plants must communicate with other cells. This is called signaling. Calcium ions are the most important messengers between cells in living things and are absolutely vital for the existence of multicellular life forms.
Appearance and Characteristics
Harmful effects:
Non-toxic and an essential metal for living organisms.
Characteristics:
- Calcium is reactive and, for a metal, soft. With a bit of effort, it can be cut with a sharp knife.
- In contact with air, calcium develops a mixed oxide and nitride coating, which protects it from further corrosion.
- Calcium reacts easily with water and acids and the metal burns brightly in air, forming mainly the nitride.
Uses of Calcium
- Calcium forms alloys with aluminum, beryllium, copper, lead, and magnesium.
- It is used in the manufacture of other metals such as uranium and thorium.
- Calcium is used to remove oxygen, sulfur and carbon from alloys.
- Calcium from limestone is a vital component of Portland cement.
- Quicklime (CaO) is used in many applications in the chemical industry, such as treatment of drinking water – especially for water softening and arsenic removal, animal waste and wastewater.
Calcium metal reacting with water, producing calcium hydroxide and hydrogen gas.
Calcium metal burning in air to form calcium nitride and calcium oxide.
