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Title: Chemistry/Elements/Calcium - Lenntech: Calcium Physical data, chemical properties, and health effects.
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Calcium (Ca) - Chemical properties, Health and Environmental effects
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Chemical properties of calcium - Health effects of calcium - Environmental effects of calcium
Atomic number
20
Atomic mass
40.08 g.mol -1
Electronegativity
according to Pauling
1.0
Mass volume
1.6 g.cm-3 at 20°C
Melting point
840 °C
Boiling point
1484 °C
Vanderwaals
radius
0.197 nm
Ionic radius
0.099 nm
Isotopes
10
Electronic
configuration
[ Ar ] 4s2
Energy of
first ionisation
589.6 kJ.mol -1
Energy of
second ionisation
1145 kJ.mol -1
Standard
potential
- 2.87 V
Discovered
Sir Humphrey Davy in 1808
Calcium
The
chemical element Calcium (Ca), atomic number 20, is the fifth element
and the third most abundant metal in the earth’s crust. The metal is
trimorphic, harder than sodium, but softer than
aluminium. A well as
beryllium and aluminium, and unlike the alkaline metals, it doesn’t
cause skin-burns. It is less chemically reactive than alkaline metals
and than the other alkaline-earth metals.
Calcium
ions solved in water form deposits in pipes and boilers and when the
water is hard, that is, when it contains too much calcium or magnesium.
This can be avoided with the water
softeners. In the
industry, metallic calcium is separated from the melted calcium chloride
by electrolysis. This is obtained by treatment of
carbonated minerals with chlorhydric acid, or like a sub product of the carbonates Solvay
process.
In
contact with air, calcium develops an oxide and nitride coating, which
protects it from further corrosion. It burns in the air at a high
temperature to produce nitride.
The
commercially produced metal reacts easily with water and acids and it
produces hydrogen which contains remarkable amounts of ammonia and
hydrocarbides as impurities.
Applications
The
metal is used in aluminium alloys for bearings, as a helper in the
bismuth removal form lead, as well as in controlling graphitic carbon in
melted iron. It is also used as a deoxidizer in the manufacture of many
steels; as a reducing agent in the preparation of metals as chromium,
thorium, zirconium
and uranium, and as separating material for
gaseous mixtures of nitrogen and argon.
Calcium is an alloying used in the production of
alluminium, beryllium,
copper, lead and
magnesium alloys. It is also used in making cements and mortar that
are used in builldings.
The
calcium oxide, CaO, is produced by thermal decomposition of carbonated
minerals in furnaces, applying a continuous bed process.
The oxide is used in high intensity light arcs (lime light) for
its unusual spectral characteristics and as dehydrating industrial
agent. The metallurgic industry extensively uses the oxide during the
reduction of ferrous alloys.
The
calcium oxide, Ca(OH)2, has many applications in which the
hydroxyl ion is necessary. In the process of calcium hydroxide
quenching, the volume of blown out lime [Ca(OH)2] expends to
double the initial quantity of quick lime (CaO), fact that makes it
useful to break down rocks or wood.
The
quick lime is an excellent absorbent for the carbon dioxide, because it
produces carbonate, which is very insoluble.
The
calcium silicate, CaSi, prepared in an electric oven from lime, silica
and reducing carbonated agents, is useful as a steel-deoxidizing agent.
Calcium carbide, CaC2, is produces when heating up a mixture
of lime and carbon at 3000ºC in an electric oven and it is an acetylate
which produces acetylene by hydrolysis. The acetylene is the base
material of a great number of important chemicals for the organic
industrial chemistry.
The
pure calcium carbonate occurs in two crystalline forms: calcite,
hexagonal shaped, which possesses birrefringent properties, and
aragonite, rhombohedric. The natural carbonates are the most abundant
calcium minerals. The Iceland spar and the calcite are essentially pure
carbonate forms, whilst the marble is impure and much more compact,
reason why it can be polished. It’s very demanded as construction
material. Although the calcium carbonate is very little soluble in
water, it is quite soluble if the water contains dissolved carbon
dioxide, for in these solutions it forms bicarbonate when dissolving.
This fact explains the cave formation, where the lime stone deposits
have been in contact with acid waters.
The
calcium halogenures include phosphorescent fluoride, which is the
calcium compound more abundant and with important applications in
spectroscopy.
The calcium chloride possesses, in the anhydric form, great
deliquescence capacity, which makes it useful as industrial dehydrating
agent and as sand whirl control factor in roads. Calcium hypochlorite
(whitening powder) is produced in the industry when passing chlorine
through a lime solution, and has been used as a whitening agent and as
water purifier.
The
dehydrated calcium sulphate is the mineral gypsum, constitutes the
bigger portion of Portland concrete, and has been used to reduce the
alkalinity of soils. Heating gypsum at high temperatures produces a
calcium sulphate hemihydrate, which is sold with the commercial name of
Parisian stucco.
Calcium in the environment
Calcium is the fifth element and the third most abundant metal in the
earth’s crust. The calcium compounds account for 3.64% of the earth’s
crust. The distribution of calcium is very wide; it is found in almost
every terrestrial area in the world. This element is essential for the
life of plants and animals, for it is present in the animal’s skeleton,
in tooth, in the egg’s shell, in the coral and in many soils. Seawater
contains 0.15% of calcium chloride.
Calcium cannot be found alone in nature. Calcium is found
mostly as limestone, gypsum and fluorite. Stalagmites and
stalactites contain calcium carbonate.
Calcium
is always present in every plant, as it is essential for its growth. It
is contained in the soft tissue, in fluids within the tissue and in the
structure of every animal’s skeleton. The vertebrate’s bones contain
calcium in the form of calcium fluoride, calcium carbonate and calcium
phosphate.
Health effects of calcium
Calcium is
the most abundand metal in the human body: is the main
constituent of bones and theets and it has keys metabolic functions.
Calcium is sometimes referred to as lime. It is most
commonly found in milk and milk products, but also in vegetables, nuts
and beans. It is an essential component for the preservation of the
human skeleton and teeth. It also assists the functions of nerves and
muscles. The use of more than 2,5 grams of calcium per day without a
medical necessity can lead to the development of kidney stones and
sclerosis of kidneys and blood vessels.
A lack of calcium is one of the main causes of osteoporosis.
Osteoporosis is a disease in which the bones become extremely porous,
are subject to fracture, and heal slowly, occurring especially in women
following menopause and often leading to curvature of the spine from
vertebral collapse.
Unlike most of the people think, there is an intense biological
activity inside our bones. They are being renewed constantly by new
tissue replacing the old one. During childhood and adolescence,
there’s more production of new tissue than destruction of the old one,
but at some point, somewhere around the 30 or 35
years of age, the process is inverted and we start to loose more
tissue than what we can replace. In women the process is accelerated
after the menopause (he period marked by the natural and permanent
cessation of menstruation, occurring usually between the ages of 45 and
55); this is because their bodies stop producing the hormone known as
estrogen, one of which functions is to preserve the osseous mass.
Evidence suggests that we need a daily intake of 1,000 milligrams of
calcium in order to preserve the osseous mass in normal conditions. This
is both for man and pre-menopausic women. The recommended daily intake
rises to 1,500 for menopausic woman.
The main calcium sources are the dairy products, but also nuts, some
green vegetables like spinach, and cauliflower, beans, lentils…
Calcium works together with magnesium to create new osseous mass.
Calcium should be taken together with magnesium in a 2:1 rate, that is
to say, if you ingest 1000 mg of calcium, you should also ingest 500 mg
of magnesium. Some magnesium sources in the diet are seafood,
whole-grains, nuts, beans, wheat oats, seeds and green vegetables.
Other important measures to prevent osteoporosis are:
Doing regular exercise (at least three times a week)
Taking adequate amounts of manganese, folic acid,
vitamin B6,
vitamin B12, omega 3 (it aids calcium absorption and stimulates new
osseous mass production) and vitamin D (it aids calcium absorption
in the small intestine).
Not abusing of sugar, saturated grease and animal proteins
Not abusing of alcohol, caffeine, nor gaseous drinks
Not smoking
Other triggers for osteoporosis are the hereditary factor and the
stress.
Environmental effects of calcium
Calcium phosphide is very toxic to aquatic organisms.
Now check out our
page on calcium
in water
Back to the
periodic table of elements
Recommended daily intake of
calcium
[ Home ]
[ Back ] [ More
Information or question on Calcium? ]
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