Thursday, June 7, 2012

Carbon - fundamental element for organic life

Carbon cycle
We breath in oxygen (O2), our blood circulation system is busy moving it to all parts of our body, and we breath out carbon dioxide (C02) or die. Green plants breath in the opposite way, taking in CO2 and breathing out pure oxygen. Isn't this a marvellous arrangement created by our God!

In Biblical times people new well coal, גּחל, but like all the other people on earth had no knowledge of the modern chemistry of carbon.

No one stops to think,
    no one has the knowledge or understanding to say,
“Half of it I used for fuel;
    I even baked bread over its coals,
    I roasted meat and I ate.
Shall I make a detestable thing from what is left?
    Shall I bow down to a block of wood?”
Such a person feeds on ashes; a deluded heart misleads him;
    he cannot save himself, or say,
    “Is not this thing in my right hand a lie? ”
Isaiah 44:19-20

"Carbon was discovered in prehistory and was known in the forms of soot and charcoal to the earliest human civilizations. Diamonds were known probably as early as 2500 BCE in China, while carbon in the form of charcoal was made around Roman times by the same chemistry as it is today, by heating wood in a pyramid covered with clay to exclude air. In 1722, René Antoine Ferchault de Réaumur demonstrated that iron was transformed into steel through the absorption of some substance, now known to be carbon." wikipedia

Carbon  (from Latin: carbo "coal") is the chemical element with symbol C and atomic number 6.

As a member of group 14 on the periodic table, it is nonmetallic and tetravalent—making four electrons available to form covalent chemical bonds.

Carbon forms more compounds than any other element, with almost ten million pure organic compounds described to date, which in turn are a tiny fraction of such compounds that are theoretically possible under standard conditions.

Carbon is the fourth most abundant chemical element in the universe by mass after hydrogen, helium, and oxygen. Carbon is abundant in the Sun, stars, comets, and in the atmospheres of most planets. Some meteorites contain microscopic diamonds that were formed when the solar system was still a protoplanetary disk. Microscopic diamonds may also be formed by the intense pressure and high temperature at the sites of meteorite impacts

In combination with oxygen in carbon dioxide, carbon is found in the Earth's atmosphere (approximately 810 gigatonnes of carbon) and dissolved in all water bodies (approximately 36,000 gigatonnes of carbon). Around 1,900 gigatonnes of carbon are present in the biosphere.

Hydrocarbons (such as coal, petroleum, and natural gas) contain carbon as well—coal "reserves" (not "resources") amount to around 900 gigatonnes, and oil reserves around 150 gigatonnes. Proven sources of natural gas are about 175 1012 cubic metres (representing about 105 gigatonnes carbon), but it is estimated that there are also about 900 1012 cubic metres of "unconventional" gas such as shale gas, representing about 540 gigatonnes of carbon.

Carbon is also locked up as methane and methane hydrates in polar regions.

Carbon and life
It is present in all known life forms, and in the human body carbon is the second most abundant element by mass (about 18.5%) after oxygen.[14] This abundance, together with the unique diversity of organic compounds and their unusual polymer-forming ability at the temperatures commonly encountered on Earth, make this element the chemical basis of all known life.

There are three naturally occurring isotopes, with 12C and 13C being stable, while 14C is radioactive, decaying with a half-life of about 5,730 years.

Isotopes are variants of a particular chemical element. While all isotopes of a given element share the same number of protons, each isotope differs from the others in its number of neutrons.

The term isotope is formed from the Greek roots isos (ἴσος "equal") and topos (τόπος "place"). Hence: "the same place," meaning that different isotopes of a single element occupy the same position on the periodic table.

The number of protons within the atom's nucleus uniquely identifies an element, but a given element may in principle have any number of neutrons.

The number of nucleons (protons and neutrons) in the nucleus is the mass number, and each isotope of a given element has a different mass number.

For example, carbon-12, carbon-13 and carbon-14 are three isotopes of the element carbon with mass numbers 12, 13 and 14 respectively. The atomic number of carbon is 6 which means that every carbon atom has 6 protons, so that the neutron numbers of these isotopes are 6, 7 and 8 respectively.

Carbon-14 is formed in upper layers of the troposphere and the stratosphere, at altitudes of 9–15 km, by a reaction that is precipitated by cosmic rays. Thermal neutrons are produced that collide with the nuclei of nitrogen-14, forming carbon-14 and a proton.


Rough diamond
There are several allotropes of carbon of which the best known are graphite, diamond, and amorphous carbon. [Allotropes are different structural modifications of an element; the atoms of the element are bonded together in a different manner.]

The physical properties of carbon vary widely with the allotropic form. For example, diamond is highly transparent, while graphite is opaque and black. Diamond is among the hardest materials known, while graphite is soft enough to form a streak on paper (hence its name, from the Greek word "to write"). Diamond has a very low electrical conductivity, while graphite is a very good conductor.

Under normal conditions, diamond has the highest thermal conductivity of all known materials. [Heat transfer across materials of high thermal conductivity occurs at a higher rate than across materials of low thermal conductivity. Correspondingly materials of high thermal conductivity are widely used in heat sink applications and materials of low thermal conductivity are used as thermal insulation. Thermal conductivity of materials is temperature dependent. The reciprocal of thermal conductivity is thermal resistivity.]
[compiled from the article on Carbon in wikipedia and the references found there]

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