|
SYLLABICATION: cal·ci·um
PRONUNCIATION: AUDIO: kls-m KEY
NOUN: Symbol Ca A silvery, moderately hard metallic element that
constitutes approximately 3 percent of the earth's crust and is
a basic component of most animals and plants. It occurs naturally
in limestone, gypsum, and fluorite, and its compounds are used to
make plaster, quicklime, Portland cement, and metallurgic and electronic
materials. Atomic number 20; atomic weight 40.08; melting point
842 to 848°C; boiling point 1,487°C; specific gravity 1.55;
valence 2. See table at element.
ETYMOLOGY: Latin calx, calc-, lime; see calx + –ium.
Calcium (symbol: Ca) is one of the alkaline earth metals
that comprise the Group IIA or S2 elements of the periodic table.
The electronic configuration of calcium (atomic number: 20) is 1S2;2S22P6;3S23P6;4S2.
- Atomic mass : 40.08
- Atomic radius : 1.74 A0
- Ionic radius : 0.99 A0
- Density : 1.60 g/cm3
- Melting point : 1116 K
- Ionization energy (KJ/mol) : I stage 590
II stage 1146
- Electro negativity : 1.04
- Flame coloration : Brick red
- Oxidation state : +2
- Abundance in earth's crust (ppm) : 3.0 x 10(4)
Calcium is extracted by the electrolysis
of a fused mixture of anhydrous calcium chloride and potassium chloride
using iron cathode and graphite anode.
Calcium being a powerful reducing agent is
used in extraction of metals from oxides which are difficult to
reduce with carbon. It is also used for removing last traces of
dissolved oxygen, nitrogen and sulfur from metals in the course
of their extraction. Important compounds of calcium are calcium
oxide, calcium hydroxide, calcium chloride, calcium sulfate (gypsum),
and plaster of Paris.
Calcium helps build and maintain strong bones
and teeth, thus protecting against osteoporosis. It plays a role
in nerve conduction, muscle contraction and blood clotting. Calcium
also appears to regulate blood pressure and may help lower the risk
for colon cancer.
Calcium helps muscle contraction (including
in the heart) by allowing proteins found in muscles (called actin
and myosin) to interact properly. By participating in the synthesis
of fibrin, calcium makes it possible for blood clots to form.
Calcium affects the release of neurotransmitters.
Calcium regulates cell metabolism, including
glycogen synthesis (the process by which glucose is converted into
glycogen). Calcium can bind free fatty acids and bile acids, which
irritate the colon. This irritation may increase cell development
to the point of increasing the risk of cancers.
In adults, osteomalacai and/or osteoporosis (fragile, brittle bones
that fracture under normal use) can result from calcium deficiency.
In addition, loss of height and premature tooth loss may exist.
If blood calcium levels are low (hypocalcemia),
muscles cannot relax following a contraction, resulting in tetany.
Symptoms of tetany include muscle spasms and leg cramps. In children,
the deficiency disease, rickets, leads to stunted growth and bone
deformities.
The adult body contains approximately 1200g
of calcium, ~99% of which is present in the skeleton. The remaining
1% of body calcium is found in the extra cellular fluid, intracellular
structures and cell membranes.
|
